Boyfriend with possible PPD

I'm hoping anyone can help,
We've been together for coming up to a year, and he's the worlds loveliest human - sometimes.
It's a tricky one as I'm unsure if he has PPD, or if the paranoia is purely cocaine abuse based, but I know he's been mistrusting ever since his first serious girlfriend cheated on him, over 10 years ago. He's 33 and an avid drug user, whilst he's high on cocaine his paranoia is at an absolute peak, he'll check windows, he'll make me check the house, he'll lay with his leg in the air aimed at the door incase anyone comes through, he told me to shush whilst stood next to the door then pointed to the hallway like there was somebody there, he even ran away from a taxi and I had to go collect him from outside my mothers house because he was adamant the taxi driver was going to harm him. This makes me think it's drug related, but he has excessive paranoia without the drugs too, I'm not sure if he's perhaps had paranoid tendencies and with the drug use he's escalated it.

The non drug related paranoia started in August, a previous partner was accused of sleeping with either person A or person B, we went to a music festival and he accused me of sleeping with a random man in the toilets, then had a full blown argument with person A. Because I stood in the middle trying to calm the situation, he saw me as trying to protect person A. Since then, there's been a collection of accusations.

- Because we were online at the same time, we were talking.
- Because I opened WhatsApp and had no new messages, I'd been deleting messages to person A.
- He sang James Blunt 'you're beautiful' to me, person A posted a popular James Blunt meme a couple of days after.
- Person A posted 'if you love them let them nap', after my boyfriend woke me up from a nap.
- Person A posted a status about his love of bread. Obviously I am the bread he was speaking about.
- Person A works as a delivery man, delivered to boyfriends work obviously to get to him.

Then came along the accusations for Person B, I'm sleeping with him because I said something that sounded similar to something he'd say, and because I stared at my boyfriends leg tattoo (I'm assuming person B had a matching one). There's also a Person C who I'm also sleeping with, no justification I just am.

Since then, it's been absolute eggshells. He went to a concert, and put his friend in hospital for mentioning Person A, I fed the dogs in the kitchen, he came in and was adamant he'd heard the back door shut, any bruises on my legs/thighs are from cheating, any marks on the bed sheets he can't account for are because I'm sleeping with people in our bed, I've been accused of closing apps when he comes near to the point if he leaves the room I leave my phone on the side of keep my thumb well away from the screen, he wanted my location turned on then decided it was useless as you can fake locations, all social media is gone because despite blocking these people months prior I was still secretly messaging them, a friend had to send me time stamps of the photo she'd taken of me asleep on her sofa to prove I wasn't out with guys, if I get a taxi to work and don't mention it he's suspicious, I can't even play music without him thinking I'm taunting him with the lyrics. He'll even misconstrue the things that I say - I once said about wanting an extra sandwich and he assumed that meant I wanted a threesome, another time I said he was incredibly fast at cleaning, so that meant he was too fast in bed.

The tricky thing to understand is he isn't a malicious person, and he isn't bad whatsoever, he's just genuinely convinced that he's in the right and I'm in the wrong, there's no arguing with him, he won't listen to reason, the only thing he's ever done is admit that he's scared of being hurt. He's broken down many times begging me to tell him the truth, even stating he's forgiven me, to tell him the truth and he'll sort out Person A B & C if I just tell him that it's all happened. I can't admit to a lie so it's a tricky predicament.
He's currently getting 6 weeks of CBT, but I don't think that'll benefit him the way it should as that was recommended as part of his drug treatment, I don't know if I should speak to his doctor and tell him about all of the paranoia, as I've sat with him in the doctors before and noticed he misses out huge significant chunks.

I can't leave him as he's my absolute best friend, and when he's normal he's genuinely the person I would marry in a heartbeat. But when he's accusing me of being awful, getting drunk and telling me he hates me and wouldn't mind if I died because I've made his life Hell.. it makes me wonder if there's any actual way of helping him.

Any advice, help, whatever please feel free to throw it my way, just know I can't walk away from a person who's hurting. I just need help on how to go about helping him fight these demons.

I know how you feel. I just broke off my engagement with someone I absolutely adore when he is not in a fit of angry suspicious paranoia. When he is well he is great, sweet, and my best friend. When he is not well, he treats me like an enemy that is going to attack and kill him. In the end, I was walking on eggshells every day not sure what would set him off. I withdrew, became depressed, and my self-esteem, which is usually quite healthy, is now having to be rebuilt. I don't know where you are because this post was from much earlier in the year. I will tell you that I stuck it out with him for 3 years. No matter what I did, no matter how understanding I was, no matter how forgiving, encouraging, loving and caring, I could not defeat this diagnosis. He is finally in therapy now, but quite frankly, he is no better than when he started. I know that everyone is different. What you just describe seems like a really big slice of hell. If I were to write about my life with my fiance, you would probably think the same. In the end, I can't live like this. I can't live with someone accusing me of things I'm not doing and treating me like I'm an enemy, bad person, nefarious planner, and malevolent partner out to hurt him. As much as I love him, I had to let him go. Only he can wrestle these demons to the ground and it will take years and years and never-ending vigilance. Once you are the target of blame, is is hard (I found it impossible) to get the cross-hairs off my back. I love him very much, but I love me more and I can't let him destroy me I hope that you find your answer in your relationship.

i have been living this hell for over 15 years now. I am just now realizing what his issues are. I have been married to him for 33 years so it is very hard to think about leaving, but I am now done, I cannot deal with this any longer. I recently figured out what it is he has and have given him paperwork to take to his doctor whom he seems to trust. hopefully he actually does it. I think he might also be on something at the times of escalation, he talks funny, like he's been drinking a lot, oh and he's an alcoholic also. it lasts for about an hour and then the slur is gone so I don't think its alcohol, but the paranoia doesn't go away with the slur. I am beyond myself as I thought we would grow old together, now I am just trying to figure out how to get out of a 33 year relationship. We were in the middle of renovations so my house is in disarray, I am going to take some money I have saved and pay someone to get it in order so I can sell it. I am getting divorce papers ready and am not going to help him. I have a nice nestegg in cash just in case, I also have an account in my daughters name, because I just cannot trust him with money. I do very well for myself and have maintained my family and household almost solely alone. he was never a father figure to the kids growing up I was always the heavy, they have much more respect for me than they do for him, as he was always a friend. I am sad for him and when he is good he is very good, but I do not like him and he has not been a friend to me never mind a best friend. anything I tell him about my life gets thrown back in my face at his next episode. I just don't know what to do for him anymore and I cannot walk on eggshells any longer. It kills me to leave him we have such great memories but these episodes are far out waying all the good times now. Very sad disease. my daughter locks her door because she think he may harm her, I cannot have that.