In most cases, it’s normal to have mild cramps or contractions (sometimes accompanied by light spotting) after sex. You’re likely feeling your uterus muscles contract when you orgasm; a warm shower, bath or heating pad can reduce the discomfort.
Be sure to call your doctor if you experience painful cramps, strong contractions, bleeding (like you have during your period) or leakage of amniotic fluid (a clear liquid coming from your vagina—you’ll know it’s not urine because amniotic fluid is odorless).