i would say if your having heavy bleeding then chances are your not pregnant but if you want to make sure id go to the doctor and have them do some blood work
Typically you don't bleed (especially heavy) when pregnant. How long have you been on birth control and do you take it properly. It's possible it could just be the hormones in the pill giving you side effects. You can take a pregnancy test two weeks from your last sexual encounter. Unless you want to conceive, be sure to use protection until your back on the pill and at least a week or so after starting it again.