How To Stop Prolonged Vaginal Bleeding After Having Mirena Insertion?

hi, i had a mirena coil fitted 3 weeks ago.ive been getting a spotting like bleeding after sex, and it lasts a coulpe of days.then on 26th dec, i had a very bad stomach ache and felt sick.on 27th i had severe pains, like contractions that you would go to hospital with(i have 2 small children).following these pains, i had bleeding which then stopped for a day.i saw my gp the following day, and he said my stomach was all normal.but im still bleeding quite heavily now,and it isnt showing any sighns of stopping.is this normal?