It could just be a UTI.
The tests aren't always accurate.
Or you could possibly have an STD. Get checked for anything soon!! STD's do usually have symptoms like that.
It could also just be that an irritant got inside of you that is irritating it. Get it checked out by a gynecologist.
The pain in your lower abdomen could just be bruising if the sex was your first experience, whether now or in a while, or if it was rougher than normal. The burning could be unrelated, pertaining to something different you had to eat, or it could be the intermingling of the sexual fluids and your urine in your urethra. Try urinating soon after having sex to clear your urethra out, and cleaning up after wards using feminine cleansing cloths you can buy at the drugstore near the feminine hygiene supplies ( they also have appeared with pads in always clean)why does my stomach hurt when my fiancee is on top when we have sex?
Its probably just a urinary tracked infection. They can give you stomach pains and make your pee burn. You should see your docter about it he will probably need to give you antibiotics.
go check if you have HIV or have the FLUWhat can I do about my stomach pains from having sex?