I don’t think I’m pregnant but what the heck?

Husband and I have been TTC and 2 weeks ago got 4 BFN followed by my period from the 5th-11th. But yesterday and today I’m nauseous with pain in my lower left pelvic area. It’s not going away. What’s going on? We had pretty vigorous sex over the weekend that may cause the pain but what about the nausea? My periods are heavy so there’s no way anything could survive or be confused with implantation bleeding. Anyone have pelvic pain and nausea after their periods? Please help! This is awful!!!