#Period Problems

I' am 20 years young .... Been having two week periods. I started on April 24th and it's been heavy... I have it today to ? Yes. 4 to 5 times I've had blood clots that are a size of a golf ball. I do NOT know why and it's unnormal for me. Anyone else had this problem or is it normal? I've had seen the doctor just a week and a half ago ... Everything seems fine. So maybe this is nothing.