Could this be it??

So at around 4pm today OH and i had sex and ever since then ive been having really bad cramps and back ache. The cramps are so bad theyve got me doubled over i even took paracetamol and had a bath at 5pm and that didnt help. Ive been timing them for just over an hour now and on average come every 3 mins and last for 40-50 seconds. Should i ring and get it checked out? Or could it just be from sex? Had the same thing couple of days ago but the cramps were no where near this bad.