Separation anxiety

Me and my boyfriend have been off and on for almost 5 years. This is the first time since we first started dating that we haven’t broken up after a few months and have actually both wanted to work things out when we have issues. Sadly, and yes I know what choice I should’ve made, but he cheated on me. even if that’s why I am the way I am now, I’m not here because of that. When we’re not together I tend to get really depressed which isn’t like me at all. I’ve never been like that at all. I actually usually like to have privacy and be by myself a lot but lately, the last few months I guess I should say, I’ve never not wanted to be near him. When we’re not able to see eachother it seems that our relationship goes downhill and mainly it’s because of me so I’ve been told. I just don’t know how to stop it from taking control over not just my relationship but me. I love myself too much to allow myself to unconsciously be controlled by my partner because of me having anxiety he’ll cheat or just doesn’t want to be around me in general which if that was the case, logically I know that’s normal because even I used to want to be alone and it not be personal at all. But it seems that no matter how hard I try I always get blamed for how upset and depressed I get from not being with him. Ik you guys aren’t therapists, but I just need some advice. I don’t think this is normal. And its slowly killing me.