How do i not compare myself to his exes

It’s driving me absolutely crazy i think about his recent ex 24/7 and it causes me to be upset and in a bad mood sometimes around him even though i know he didn’t do anything wrong. I’m constantly thinking how much prettier she is, skinned she is, has bigger boobs than me, cooked for him, took care of him when he was going through a tough time. And she’s still his friend, not as close. I kind of do the same things for him like take care of him and buy him food and we have a lot of fun together and he sleeps at my place a lot. But i can’t help but think she took care of him BETTER than me. She fed him MORE than me. She’s nicer than me. It’s fucking me up and i hurt myself really bad yesterday because these thoughts won’t shut up. How do i stop comparing myself to her?