Early labor at 30 weeks? Im 16 yrs old and 30 weeks pregnant

Im 16 yrs old and 30 weeks pregnant today. and ive been having horrible stomach cramps, like i have to poop. But when i go to the toilet i cant poop, but im not constipated, because when i finally do poop its soft like diarrhea almost. But even when i go to the toilet and just push a few times, whether something comes out or not, i feel a little better until 20 minutes later when i lay back down. the same thing happens!
this has been happening for about 4 days now. i read online that it could be signs of early labor. but i don't know what to do.
Also, it started happening after me and my boyfriend had very rough sex, and hes really big so im pretty sure he might have hit my cervix a few times.. and i was on top too so im wondering if the bouncing might have caused anything too...
there's also been an increase in discharge, but its not more liquidity or anything its still thick discharge, just more of it. and there hasn't been any blood. or heartburn or back pains.
(my stomach has been harder then usual but i can still feel him wiggling around all the time)

i really don't know what to do. please help im scared :/