My baby is 1 year old.I had my 1st period when she was 6 months old.it lasted for 40days.then I missed my next month period.but after that I had my periods but its heavy.it last for more than 15 days.is it normal to have heavy periods after birth for so long?

It can be... but you may want to check with your doctor for the reassurance. Some women find their cycles change after having a baby and they find they have a new norm.

True, my periods changed after my daughter, your body changes so much period... but get it checked out 15 days does seem a little long especially for heavy bleeding. Are you taking any new contraceptive? Go to the doctor anyhow and best wishes.