Worried/ Concerned. Depo Shots & Bleeding.

Hi i am 18, so i got my first depo arond feb-march 2010 after the.. after-pregnancy bleeding stopped.. (my first child was born in jan.) everything was going well. no bleeding, a little spotting i thought everything was ok. going in for evey depo shots. then around sept-october, i started getting a period. it lasted about 2 weeks.. so i stopped getting depo shots altogether because the cramps were very painful.. coming to the end of the year around november december, christmas time. i got my period alot, at very random times. just when i thought it was finishing, it would come back in full force being very irregular. i bled full on for around 3 months plus. i went to see the doctor and she said my body went into shock or something and just bled. so she recomended to go back on it. so i had my first shot in may 2011 which i was happy to have just to stop the bleeding. it stopped for around 2 and a half weeks and has started up again in the end'ish may. i got depo injection two weeks earlier than usual..(7th july) cos of the bleedings, it is now july 9th and its still very heavy, sometimes slows down and heavy again which is VERY fustrating. i need to know if anyone can give me some advice for this or if it happens or happened to them. also havn't done a full check down there, i am way to shy. i also have concerns about my health because of whats happening and the awful an weird cramps ive been getting too.