Why am I bleeding on the pill?

[venusx5]

Hi everyone haven't messaged since I had my last appointment with gynaecologist, been told cause of my age and the fact I want to try for babies soon the best thing to do is take the pill solid for 3/4 months then have a period to help with my pains, almost finished the 3rd month but for the last 2 weeks I've been bleeding some days heavier than others and getting extremely bad stomach cramps and back pains. Is this normal? I'm not sure whether to stop the pill of to keep taking it although it doesn't seem to make a difference by taking it daily as I'm still bleeding