I’ve become so insecure. Help please..

My bf and I had had a slippery slope in our relationship. We weren’t talking for almost 2 weeks I think. Now that we’ve fixed things, I feel so insecure. If I see him walking with someone else or texting someone, I get this feeling inside that I’m not enough. He tries to reassure me but idk ): I feel ugly and like I’m not enough. I feel like he could easily find someone way better than me & I know my insecurities are pushing him away. How can I cope with it? I used to be so confident and so happy with myself but now I work basically all day and I’m so tired that I don’t have the motivation to get cute, dressed up or do anything to make myself look decent. I wear basically the same thing all the time. My self esteem has reached an all time low and I’m constantly second guessing out relationship because I’ll start thinking he’s gonna leave me for someone better