throwing up/diarrea after sex

Hi ladies, this never used to happen to me, but recently after sex i have been feeling really sick to my stomach. Tonight I threw up twice after having sex. Two nights ago I had a similar feeling, but I ended up having diarrea which ileviated some of the pain. I read somewhere this feeling is due to the man continuously hitting the cervix, but I was just curious if you ladies had any helpful advice on how to avoid this awful stomach pain in the future?