What Causes Brown Spotting,vomiting And Back Aches During Cycles?

Hello, I ve been having strong pregnancy symptoms. It all started 3 week ago after the guy I had sex with ejaculated inside of me. I waited 4 days before taking a at home test and both came back negative. Later that day my period came and it was heavy. That period was short and I began to spot light pinkish and brownish for 2 days. But now I ve been having morning sickness, backaches, headaches and actual vomiting. Weird smells make my stomach turn and I can t sleep at night. What is wrong with me. I take birth control so I doubt I m pregnant