Could this be fatal?? :( very important! plz help!!?

Well I'm a teen so I kinda have to sneak around with my boyfriend but...on march 22 we had sex without a condom & 4 days later I got a lot of brown discharge that lasted about 4 or 5 days. I started haveing really bad pains on my lower stomach, sides, & lower back so I told my mom exactly a week after the sex. The next day she took me to the doctor to get a pregnancy test and it came out negative but it was only a week after the sex. I got the Depo shot for birth control but still had pains for 2 months. During may I took another home pregnancy test & it came out negative. I didn't get my period for 3 months after the shot (march through the middle of june) but I finally got it 3 weeks ago & I'm STILL on it to this day. I've gained 15 pounds but it isn't showing anywhere on my body....About 2 weeks ago I tried haveing sex in a hot tub with my boyfriend (yes I was on my period but it was light) & his penis wouldn't go in longer than 2 inches & if we tried to force it, it would hurt both of us SO bad! It was like something was blocking it so it couldn't get in. Anything longer than a tampon won't go in even if I try to force it....could this be fatal?? What do you think is wrong with me???