Bdp or me?

I was diagnosed with bpd years ago and it was all under control and had been ever since i moved in with my partner 7years ago. It never went away but i controlled it rather than it controllong me.
That was untill approx 3 weeks ago when my partner went to the uk to pick up some bits for the house. Firstly i hated being on my own even though it was only for a couple of days. On the last night he was away he did not answer his phone all night and i thought something had happened to him. He called me the next day and said he didnt here his phone and he was out with old friends that the hadnt seen in years. He implied that i was being stupid after seeing all tge missed calls.
A few days after he came back he showed me a pic of a man and told me he thought it was his son. This then led onto all the things that are wrong with our relationship, to the point where he said if im not happy i should go. If he could have a secret son and decieve his former wife surely he could do this to me to. So when i then found out that the day he didnt answer the phone he was with the mother of this lad i couldnt deal with it Since then i have been really low, followed by depersonalization, followed by self harm, then low again and actually ok ish today.
I totally closed down to him. I resent him. I cannot communicate with him not because i dont want to but i just sit there while he talks to me about this situation and i just say "i dont know" to everything. I have always done this with things i find akward to discuss even though i wish i didnt. I tried telling him its the bpd stopping me communicating but he keeps saying its not the bpd its me playing games. This really hurt. Now i cant stop thinking about this - is it really me and not bpd? I cant answer the question because i dont know the answer but if he cant understand the bpd how can we continue?
Now i am thinking - why the hell cant i just talk? Cos i do know what i want to say but i feel intimidated when he trys to talk to me. I suppose part of me doesnt want to get to the - you should leave - bit of the conversation so my brain thinks its better not to talk.
This probably isnt making sence.
Hes going away again probably next weekend for a dna test and staying with the lads mother. Says i should trust him as their relationship was many years ago.
Firstly i dont want him to go and secondly i dont want him to stay there. What if they realise they still fancy eachother?
Getting very parinoid about all this.
I can see that i am gonna be getting very low again when he goes. I cant tell him he cant go cos he needs to sort this out and i should be supporting him.
How can i just stop thinking irrationally and just trust him? How can i trust anyone?
Wish i was normal!

Oh geeze, I feel really bad for you, having to go through this. It's really hard to give specifics, as you could be presenting a one-sided, distorted view.

But. . . . . Just the facts here, leaving out the opinions, I completely understand how you feel. You have every right to be hurt here and even more right to be hurt if he's staying with that other woman.

Keep taking each moment. You'll make it through. If he's telling the truth, it will work out. If not, you're going to be better off anyway, but it's so hard to see that when you're in this spot. None of this seems any of your fault. Guys like that, people like that, you can't fix them.They have to fix themselves and odds are, they don't want to and never will.

Hi, sorry you're feeling so bad.

If you can't communicate cause of the BPD have you tried sending emails to each other or writing notes? It can help with that sort of thing. (can write him one to ask him.) If he's unwilling to try to work round it in any way or consider the possibility you're trying, that particular problem is him not you!

Considering the BPD, while you need to be able to trust him, it also does seem fair if he makes small adjustments to things - staying with an ex is a lot to expect when you feel insecure about things, i think if you know him to be trustworthy, maybe you should be able to trust him, but not everyone is the same that way, lol) but also feeling uncomfortable with him staying there is perfectly reasonable and i think it would be more appropriate for him to stay in a hotel on his own or something, especially if the son is there and they don't have the results yet. just a personal opinion tho.

Hope the two of you manage to work those things out.