weird cramps, heavy boobs and back aches??

Frankie
Okay so I've been having period like cramps (very bad ones I might add) since I had sex about 3 days ago. I had unprotected that time and a few days before then. Is it just from my fertile window making me cramp from ein sensitive or something or something else??? Like my boobs are heavy too I don't know what the hell is that normal????