Do you feel insecure in your relationship?

I never had an issue with that, I felt secure in my relationship until a few months ago. Since then I cry at least a few times a week, I keep thinking why is he still with me, I keep comparing myself with other women that he knows or he’s been with etc. I never had a good image about myself, I’ve always struggled with depression and things like that but at least I felt secure in my relationship. But now for some reason I’m feeling so low that I’m starting to reconsider it and think it might be better for myself if I stay single for a while so I can work on myself.... I don’t want to break things off, we’ve been together for 3 years and he’s my first serious relationship. I love him dearly and he treats me so well, but my dark thoughts wouldn’t leave my head. I keep thinking I’m not pretty enough, I’m ugly, I should lose some weight, my skin started breaking out like crazy these past few weeks because I’ve been so stressed out and it just makes me feel worse; we haven’t had sex in over a month because of how gross I’m feeling about myself. I feel like I’m ruining everything because I know it’s all in my head but I can’t help it. He’s there for me and reassures me that he loves me but my head still won’t take it... I’ll be fine for a day or two then go back to square one, hence the reason why I don’t want to talk to him about it because I don’t want to put pressure on him and push him away... I’m just so done with myself I just needed to vent 😔