brownish discharge after sex during pregnancy.

I am 22 years old and have been married for about 2 years now. My husband and I are having unprotected sex to try to conceive a baby. Last night we were having sex, but it lasted longer than usual and it got a little rough...nothing abnormal...just harder thrusting. Well, sometimes he can go too deep and hit a really sensitive spot that really hurts...and sometimes leaves me with sharp, intense cramping for sometimes an hour at the most. I have gone to the gynecologist several times about the problem. They have palpitated, x-rayed, had a couple ultrasounds, abdominally and virginally, and they say I am fine, it might just be gas. The weird thing is when I have those cramps, I get gassy and it feels like my anal cavity hurts just as bad as where the front abdominal cramping is, take note we do not take part in anal sex. I am 2 weeks late for my period but have not taken a pregnancy test, which brings me to my concern. After we got done having sex last night, I had a mild version of those cramps, and woke up this morning to find a brownish pinkish discharge on my underwear, not a lot, just 2 quarter size spots, liquidy and not thick with no odor. I am feeling fine now with the normal dull aches I have had for 4 weeks now following my ovulation and have only clear egg white discharge, normal amount. Is there anything I should be worried about? Please help!