Shooting pains in uterus ?

i recently got my implant took out about 2 months ago and for the first time the other day i got this major pain during sex when my bf was doin the business lol.. but it hurt alot and i never got this before with him. i have 2 children and these pains were like labour pains the last 3 times now we have had sex its happening my uterus gets shooting pains and cramps and can barely lift my leg to walk.. i went to the doctor and she said i had a urinary tract infection but im just finished the antibiotics and is still happenin i also get this pressure feeling in my bum and my back does hurt aswell :(.... has anyone went threw this ?