Yeah, it is super normal. If from an orgasm or an intense sex scene, it may be the rush of various chemicals in your brain, and like according this article, 46% of women have experienced “postcoital dysphoria (PCD)”, which psychologists call the idea of the feeling of anxiety, depression and tearfulness, post-coitus. It is triggered as a result of a release of chemicals from sex.
Basically – it is super normal. I suggest you read up on it.
Oh yeah, it is super sexy too. Especially to me. If gives a man the opportunity to say (a) know you fucking rocked her world, and (b) allows you a unique opportunity to hold your woman as she cries, be there for her, let her know you give a fuck about her, and not have to solve her problem.