It's not uncommon.
According to a 2015 study published in the journal Sexual Medicine, crying after sex (known as post-coital dysphoria or PCD) is a bit more common than one would think, at least in college-aged women. The research found 46 percent of those surveyed had cried at least once after sex, while one in 20 surveyed had felt the post-sex blues a few times in the past month.
that part of the reason for PCD could be chemically based. “Especially for women, sex and orgasm can release the hormone oxytocin, which facilitates attachment and connection,” But, especially with more casual sexual encounters, there can be a disconnect between the chemicals signaling attachment and the fleeting reality of the situation.
While study authors suggest that PCD doesn’t correlate with intimacy in a relationship, don’t dismiss it altogether: The reaction can be reflective of issues in a relationship (although, sex is one of those totally normal things couples fight about). that more research is needed on the topic, but recommends seeing a sex therapist as a possible avenue to addressing the experience