I've been on the pill for over a year now for the first time I've had a heavy period, Could I be pregnant?

Pregnancy is possible while on the pill, but as long as you have taken them on schedule, you most likely are not pregnant. A heavier period than normal is not really a sign of pregnancy. Periods can be off from the norm now and then and the pill is often a cause of changes in periods, even if you haven't had a change before.

If you have missed some pills here and there, and even if you haven't, you could try a pregnancy test for the peace of mind.