Hi, I'm 21 Years Old African American 5'0 Feet And

Hi, I'm 21 years old African American 5'0 feet and 130 pounds. I'm usually healthy. I take birth control and some medications. I been having extreme dizziness, vertigo, nausea and menstrual cramps, along with a period like flow but it's brown in stead of red. I recently took a pregnancy test and it came back negative. This is really debilitating, and I could use some guidance to figure out what it is.