Feeling insecure in my relationship, advice?

My boyfriend and I have been together for almost a year, we’ve never argued and everything is going great between us. We both have a past of depression, self harm and all that. I’ve been feeling a lot better in the past few years, however because of his past relationships he does get insecure. He’s been cheated on and been in an abusive relationship for 2 years which made him fall in an ugly hole of doing drugs for another 2 years but he hasn’t touched anything since before we met. He always tells me I’m the reason he’s alive and I gave him a reason to stop doing what he was doing, that he tried quitting many times before but always fell back into it but when he met me he knew he had a reason to stay clean. He often cries on me because of his past and his insecurities, thinks I can do better than him, that he’s got fat and that he doesn’t deserve me. I always hold and reassure him he’s everything I want but I understand where he’s coming from because I have my own shit I deal with. Insecurities, don’t think I’m worth it, I hate the way I look, I sometimes compare myself with his exes because they’re skinnier and prettier than me but I don’t really tell him about it because I know he’d worry. As I said, we’ve never fought, I’ve never doubted him until a few days ago when my insecurities got the best of me. Maybe some of you remember my post in which I asked if you’d find is suspicious if your SO had his snapchat notifications off. Well I couldn’t help but overthink even though I kept telling myself he wouldn’t hurt me like that and he told me it was because of some group chats that I know are active and keep popping up all the time. He never hid his phone from me, he goes through his phone and messages while I’m next to him looking at his phone. The next day I saw him and he just casually opened snapchat, I saw it on his friends list that his only two best friends are the group chat and some other girl he’s told me lots of bad stuff about who reached out to him because she’s about to be homeless and he waa trying to give her some advice but she ignored it so he stopped replying. That put my mind at peace and the day after I told him I found it a bit off and he told me he has nothing to hide from me and if I ever doubt him I can just ask him for his phone and he’d gladly give it to me. He also turned his notifications back on to put my mind at peace. He doesn’t have a mom, only his grandma and he talked to her about it and even she said she knows how much he loves me and that he wouldn’t do that. But my stupid ass head still can’t help but overthink all this crap. I was looking last night on the snap maps and he was active on it for over 2 hours, constantly which made me think all sorts of stuff. He literally proved me I have no reason do doubt him which I knew I didn’t but my head won’t stfu and I overthink everything. I also feel like I’ve destroyed everything by telling him that I had a little doubt. I can’t help but feel like shit about everything even tho I have no reason to 😔