Seriously, I am driving myself insane trying to be a "normal" girlfriend.

My partner and I have been together for almost two years. I love him so much, but we live together in a small apartment and the pandemic has really taken a toll on both of our mental states. When he's not happy, I automatically think it's because I'm not good enough, even though he has told me it was nothing to do with me, it's just being cooped up inside all day. For the first year and a half or so we were fine, but now that lizard part of my brain is starting to take over again and every time we have a conflict or bump in the road, my mind goes "RED ALERT: IMPENDING BREAKUP APPROACHING" and then I spiral into frenzy of anxious thoughts that won't leave me alone. 

He knows i have anxiety but he's never had it himself, so even though he tried his best, it's hard for him to know what to do when I have an anxious meltdown or panic attack. And now my anxiety is telling me that I'm not good enough for him, he deserve better than me, my mental illness is going to drive him away. I can't even go on a simple date with him nowadays because my anxiety is in overdrive and I'm constantly thinking "oh gosh I hope this is going well, oh no I can feel some tension between us, oh wait actually it's okay I'm having a good time, oh wait look there's a girl over there way prettier and skinner than me who's probably actually normal, he deserves to be with someone like her, I'm so fat and ugly compared to everyone else..." etc etc.

I can't get these thoughts under control and it is tearing me apart. I feel so bad because he feels like he's doing something wrong and I can't convey exactly how I'm feeling because as much as he tries, he doesn't understand.

I don't want my mental illness to be the demise of a relationship that makes me happy. He's everything I could want in a partner but I can't reign in the thoughts that he deserves better than me.