This is a tough thing to decide. I've done both. With my previous BF, I let it all out, told him everything. For me, it was the wrong thing to do. I don't know if it made him dislike me, or if I just assumed he would because I showed him my worst side. Anyway, I became very paranoid, started acting like the person I was describing but full time instead of only part time. So ultimately he couldn't take me anymore and left. I'm in a new relationship now. I took the opposite tact at first. But it's kind of hard to hide the fact that I am in therapy 4x/week. So I let him know small details bit by bit. I tried to normalize them though. For example, I could say A)"I'm depressed 24/7, periodically SI, have frequent suicidal thoughts, have wild emotional swings and suffer from abandonment issues and other Borderline personality traits." Or - I could say B)"I'm suffering from PTSD due to some issues in my past and how my ex treated me but I'm a whole lot better than I was a year ago and the therapy I'm in helps me so much with my relationships so I think it's a huge positive. So I'm just telling you in case you see a scary person show up every once in a while. I'm going to try my best to keep her away from you". So in the first post marriage relationship I described above, I essentially did the first (not all in one sitting mind you) and it was a BAD idea. In the second (current) relationship, I did the second. It is totally the right thing for me. It's like I'm painting the situation in the best light possible, not overdramatizing it, not trying to get sympathy or lean on him, just telling him what he needs to know so he can just try to be patient and understanding when I'm suffering from my issues. So basically I try to word things in such a way that it sounds like I'm an OK person to be around. And it puts me in a much better head space and also makes me a lot less paranoid about abandonment.

I hope this makes some kind of sense. I wish you the best.