Boyfriend says sex makes him sad

I took my boyfriend's virginity. We have been together for 2 years and we were 19 and 20 when we had sex for the first time. He would always get teary eyed after having sex and he said sex just makes him emotional but he told me he actually feels really depressed after sex and he doesn't know why. It just makes him sad. I asked if he hates sex with me and he said it's not that and it's fine in the moment but after cumming he gets washed with depression and it's why he doesn't like having sex often. Am I doing something wrong? Am I not tight enough for him? Am I not attractive? How could sex with me make him depressed?