Mom Is Dating My Ex-Boyfriend

I'm a twenty three year old woman & have severe anxiety and OCD that are both under control currently. I'm having a hard time though not being pulled back into those with my life right now. My mother is dating my ex-boyfriend, who was my first serious boyfriend 2 years ago and is my age. We'd intended to marry one another, but I eventually broke it off when I felt we weren't right for each other. But I still was very close to him and have this visceral disturbance by them dating. No matter how many times I talk this over with my mother she doesn't seem open to seeing my side and how hurtful this is for me. She says I should just be happy for them both, its my problem, I wont stop her from being happy etc. When its in my face though I cannot help but feel horrible. We had an amazing mom/daughter relationship that seems gone. She acts catty toward me now like we are in competition (which we definitely arent I do not want this guy back) and very secretive and will scream at me if I object to whats going on. I've asked that at least she not talk to me about their relationship so often and to not have him over so much, but that only lasts a few days and then it's back to hearing ten thousand things about him and me being trapped in my room because I don't want to be around them in my home. I would move out but I'm saving for college and could never afford it right now. How should I deal with this situation? I've tried talking with a therapist but it's so uncomfortable to bring up, I feel a judgement toward my family so don't want to discuss it. Friends and family I can't really go to because a lot of them would just gossip about it which I would hate to have happen. I feel really sad that my relationship with my mom seems marred and changed for good. Also helpless because neither of them seems to care how this is effecting me. It's sad, he used to be my best friend and now having him around this way is just harmful to me. But I get sucked into feeling guilty not wanting to make them feel bad so I don't do or say more. Does anyone have any advice or thoughts for me?

While I have never been in exactly your position, I do know what it feels like to have my mom date someone that was my age, interested in me and then became just about a permanent figure in the family.
I came home from a yr away and this guy was interested in dating me, but I thought he was a little fast and I was having some depression stuff myself. So, because my mom and I worked in the same place, he started talking to her. She was married to my stepdad - we had a great family life I thought (I was away at college so a lot might have happened) but my sister and brother were there and I didn't think anything was wrong. Well, two months later my mom takes up with this guy all the time. He spends the night over, they are drinking together and seem like they are getting along great, even with my stepdad. I still was like... ok... whatever.
Another couple months, she leaves us all and moves in with him in his gross cabin of a house the day after christmas. I was grossed out and furious with her. I can understand your feelings of betrayal in this way (albeit not in the same sense since you were in love) and of frustration and anger. I couldn't imagine my mom would do this to us and to expect us to treat this man like family because she decided to be in a relationship. I didn't speak to her, and I moved out as soon as I could. It took years to recover our old relationship - and honestly, it still isnt the same. She acts like she is 15 and I am her mother. She calls me now about her latest bf (she left the first guy after four yrs) and asks me my opinion about her life with him, sex advice, etc. I don't like it, but I have done some work on myself and realized my relationship with her will never be the same. She isn't the mom I had when I was younger, the one that took me to girl scouts and taught me to value myself as a strong woman. She isnt the same, and I am having to draw up new boundaries and create a new relationship while mourning and valuing our old one in my own way.
I know this is long, and I hope it relates somewhat. I was fortunate that I had a sister that I could talk to. But I totally get not wanting to talk to friends, believe me it HURTS when they start saying stuff. And I have been wary of therapists too, just because I am scared the floodgates will open.
I am here though, and although this is my first post on here, I could relate and wanted to say you are in my thoughts and I know it is hard. You are a good person and you are reaching out to others, I applaud you for that.

Thank you so much for all you said.
It sounds like we are quite similar. Especially with not being able to believe your mom would act that way. It's such a shocking thing to feel like this person you've always known is now almost a stranger based off their actions. Also the feeling like you're parenting your mother. I've read a bit about that and definitely identified with it.
I tried discussing it again today and she just put the blame on me for trying to ruin her life, which I certainly am not, I don't want her to be hurt ever. Overall I got the messege that hes a priority way over me, which might sound babyish, I don't mean it to, just feeling that a parent (especially one I was so close to) continues to make that kind of choice is awful.
Its comforting to read that someone else understands this feeling, though I hate to think youve had such unsettling stuff to go through as well. I hope you continue to heal from all that went on.
Again thank you so much for your post, it's helping me feel less alone in all this

Dear you,
You wrote this in 2012 and im sure lots have happened simce then...but I just HAD to tell you that it is absolutely normal for you to feel this way!... what your mother did is a great betrayal... she failed you as a mother, no doubt about this here. It is hurtful just to read you... that she wou”d dare making you feel guilty about it on top of it. The good news is, it is crystal clear that she cant be your mother, as she should be..and therefore trust your guts... there is no room for doubts..
Be brave. Be better.

I imagine how difficult it is for you. you should talk to the expert about this.