What Causes My Periods Getting Longer?

I am 17 and have very long periods. This first started when i was 14 and was on my period for 4 months but was not registered to a doctor. After a while my period became regular again but at the start of last year i had the contraceptive injection that caused my period to last 6 months, my current doctor gave me tablets that i cant remember the name of, i could only take these 5 days at a time. These were working really well for me but i then got told i could not take them anymore and i got moved onto microgynon 30. Now my periods are very long and irregular and i have currently been on my period 2 months. I cant go on like this as i am constantly feeling ill and it is affecting my college life which involves a lot of sport. I also suffer from anemia and have been asked to do a pregnancy test, a chlamydia test and countless numbers of blood tests. Is there something seriously wrong with me? xx