Pain In The Lower Abdomen After Intercourse, Difficulty In Urination, Reduced Urine Output. No Periods. Concerned

I slept over at my boyfriend s house a couple of night s ago and we had unprotected sex. Immediately after, I started having horrible nausea and stomach pains, almost like I was about to get my period, and it WAS that time of the month... But I didn t. I woke up in the middle of the night, covered in sweat and very uncomfortable. The pain subsided the next morning, but grew WORSE that night when I realized that I could not urinate properly. When I urinate, my urine is a light, pale yellow or clear and it has decreased significantly in quantity. I will start to urinate and it does not burn until I am almost finished or finished - or so my body says. I stop urinating but it still feels as though there s more left, however, it won t come out! I feel a hard pressure in my lower abdomen , where it feels as though I have to push to urinate further - but I still cannot. When I m not using the restroom, there s a mild pain in my lower abdomen, my lower sides and lower back - I still have not gotten my period and am beginning to get worried. What should I do and what could this be? :(