please need advice!!!

I think I might be going crazy?! My period ended on the 5th and it seemed normal to me. The past week I've been feeling very off! I don't get it because I got my period why would I be feeling weird? I keep getting pain in my breasts and almost like a pulsing feeling "down there". I'm cramping (never happens unless my period is close) heartburn, gassy and getting little feelings in my stomach. I've never dealt with this before help?? Even if I did take a test wouldn't it be negative because I just got my period? How could I even be pregnant when I had my period?