Not my normal!

Been talking with my boyfriend for a couple months about having a baby and stopped my BC about a week and a half ago. I was initially on it to regulate my cycle, and every time I get back on it, it takes about 4 days for my period to resume. I got off of it Friday the 11th. And had unprotected sex Wednesday the 16th. More than once. Then on the morning Sunday the 20th, I started what I believe to be my period. Its a pretty medium flow. No change in color but I next to never have any side effects other than ovarian cysts and headaches. I have had terrible back aches and awful abdominal/pelvic cramps and my boobs and nipples are sore and my lady parts are kind of tender. Has anyone else had issues like this? When I started bleeding I was super upset and I honestly don't know what it is. I think it's my period but others have said I may be pregnant. I have yet to test, just want to hear some opinions.