PLEASE PLEASE PLEASE I need advice. In October, I got into a relationship with this guy who is currently my BF. We've been together for 3 months now, and we've expressed that we're both really happy in the relationship together, and he knows how to handle my BPD really well which is helping me see an improvement in my mental health (but of course I have medication and professional help too). He makes me really happy and I love him, but I can't stop obsessing over his ex. They broke up before he moved away to college because they didn't want to do long distance, but that's the only reason why. Upon moving, he still wasn't over her and he would talk about missing her and all that when we were just friends. A few weeks later, I heard from one of my friends that he was interested in me but all my friends were warning me not to date him because they felt like he wasn't over his ex.I let it slide and I still decided to pursue the relationship. It took about a month for me to pass her on his best friend list on Snapchat and every time we hang out he's getting texts from her. She randomly decided to follow me on Instagram a few weeks ago, and her most recent post is from august where they're making out and the caption is "not a goodbye, but a see you later". Obviously, this is triggering my anxiety so bad and I can't help but worry that something is still going on between them. I brought it up with him about a month ago and he promised me there was nothing and he got rid of the hearts next to her name like I asked. It calmed me down for a few weeks but now my anxiety is back up after seeing the post and they still talk like all the time. Last night I had a breakdown in front of him because of how much it was stressing me and he assured me again that he has no feelings for her and that he's 100% dedicated to me and only me and doesn't want anything to do with her. He asked her to take the post down about a week ago and she still hasn't done it. He claims that she's interested in someone new but I can't help but feel like she's trying to provoke me.

Sorry for the long post, but I'm not sure how valid my feelings are at this point. Even thinking about her makes my blood boil and if I could I would gladly crush her skull in. My favorite thing to do is insult her shitty posts with my roommate who also has BPD, I get so much satisfaction out of insulting his ex and I wish I could do everything in my power to make her feel like absolute shit (but I've been keeping myself from doing it because I know it's part of my BPD). At this point, after my BF has been so kind and reassuring, I don't know if my anxiety is even valid anymore, or how to stop it. I can't get his ex out of my mind, I feel like I'm basically obsessed with her, and I feel like I'm competing with someone I don't even know.

Does anyone have any experience with jealousy when it comes to your partner's ex's and how were you able to calm the anxiety down? I feel like this is the only obstacle in our relationship right now, and it'd be great if I could just forget about that bitch cuz I literally want nothing to do with her, and I don't want to cut my ex off from her because I know that's toxic.