I just finished having sex and im experiencing mild - severe cramping in my extreme lower abdomen. It almost feels like period pain. It' hurts to move?

See doctor. Sudden onset of pain is concerning, especially if it is severe! if you are still having severe pain, you need to go to the emergency room.
My 1st answer-males. Possible: uterine cramping common like mild period cramps common after orgasm. Right-sided pain with fever/nausea/vomiting may be brewing appendicitis. Std with pelvic inflammation causes generalized lower abdominal pain. Ovarian cysts can burst or ovaries can twist and become torqued causing severe one-sided lower abdominal pain. See a doctor asap. Torque and cause one-sided pain.