whats wrong with me

hi I'm 20 and had 2 miscarry s back to back, one January 1st and February 17. took birth control for a month then we decided we were ready for a baby. since march "when i stopped taking birth control" my periods have been strange. the doctor told me they would be messed up due to the birth control. I don't understand this because i was only on it for a month exact. It is now June and i just had my 3rd miscarry...i am healthy take a prenatal everyday does anyone have any ideas......it is truly heartbreaking and sets me back a little