3 periods in the last 4 weeks

I am 17 and I would like help understanding my periods. 5 weeks ago I was given a pill to make me start my period because I was 2 months late. I started a week later and ended after 7 days. I had also started the pill that sunday I was on my period. Exactly a week after I had ended my last period I started again, only this time it lasted 11 days. It is 4 days later and I have started again! I really cannot take this anymore and need to know what is going on. I started the pill because my period would always be 2+ weeks late or months. I didn't expect to get my period 3 times in 1 month though. I also get CRAZY mood swings that drive me and everyone I know insane. They have begun to continually get worse too. I just don't know what to do anymore! I keep feeling weak and I have horrible cramps. Not to mention my legs went numb almost a week ago and they still give me trouble especially with stairs. Is this due to my period? I dont understand.