has this happened to anyone ?

I attempted to start birth control , I took it for three days for the weekend of Memorial Day weekend , I decided to stop I didn't like the way I was feeling on it . Since then I have had two periods . In a matter of four weeks . Every other weekend I have started a cycle . I am currently on the second day of bleeding I am in serious pain , left side of my pelvic only , it comes and goes yet when it comes its super painful . I am bleeding heavy , and clots , has this ever happened to anyone . I took a test and it was negative so I can't be pregnant