Pink butterflies if I hadn't known better I would have thought I wrote this. I am having exactly the same issues at the moment. I have always been EXTREMELY jealous and we all know how destructive that can be to a relationship. There's only so much reassurance a partner is willing to give, I've been with my Boyf a year and his patience has just run out. His friend about whom I have similar thoughts to you is his ex!!! He still sees her regularly and texts her almost daily. He goes round hers and does things for her, just over a month ago we temporarily split and he said he still had feelings for her! A few days later he begged me to come back telling me that he missed that life not her???!!!! I'm not convinced at all and I am all consumed by these thoughts now. My day consists of judging his every move to try to get to the truth, our relationship used to be amazing up until four months ago, his ex started to date, things changed dramatically. He swears on everything dear to him that he doesn't have feelings for her, I'm imagining all sorts and literally suffer a panic attack every time I know he's with her. So a slightly different situation to yours, by the sounds of it I have a lot more reason to suspect, I mean that as in it sounds to me like your trust hasn't been tested too much, I think it may be the bpd causing you to think irrationally, from what you have said anyway. I on the other hand am also very jealous and paranoid both of which becoming extremely hard to cope with, but my paranoia and jealousy has been fed, by his comments and his refusal not to see her as much. If I could give you any advice I would say try as hard as you possibly can to trust, unless you have sufficient evidence it's unlikely he's cheating. Try not to keep asking for reassurance, try to refer back to his previous efforts to reassure you if you can, constant seeking of reassurance is draining and destructive and patience will run out. It's a downward spiral, try to stay positive and look at all the evidence to support the fact he's not cheating, I'm sure there's plenty. Stay strong and stay positive pink butterflies.