Is this relationship a mess?

So I have a severe eating disorder, anr severe self esteem issues. My boyfriend (M32) and me (F20) have been together for about 5-6 months. Recently, my ex confessed he still had feelings for me. My boyfriend got rly angry about it. We have a screaming match and anyway he ended up showing me photos of his girlfriend, who he talked up so much. All I think is that she is 3 dress sizes small than me (I am size 6, and lost 5kg in past 5 months after being with my bf), and that she’s extremely better looking than me. I now literally can’t have sex with my boyfriend without it hurting. I feel so unattractive and undesirable now. I told him “I can’t have sex because I have no energy from having an eating disorder.” But it’s actually because I feel so ugly and undesirable. I don’t feel like he should’ve showed me photos of her.

Edit: I’m talking Aus size 6, so US size 0, or universal size XS.