Chances of pregnancy when you no longer get a period on birth control

Alina
So I've never had regular periods my whole life. When I started birth control last year I started getting them regularly even though they were shorter and lighter. That was until a few months ago when I stopped getting them or would just have some spotting or discharge. Two months ago I didn't get it and only had cramping. I have recently become sexually active and I'm worried that I won't be able to tell if I'm pregnant or not because I no longer get a real period. The doctor says this may be a side effect of the birth control. We haven't used protection because I am on the pill. I had sex a few days before my period was due two weeks ago. I didn't get my period or have any spotting or cramping that cycle. Now I'm worried I could be pregnant because I've been having some cramping...not sure if that's related to the constipation that I have been dealing with lately as well. But that seems to be my only symptom at the moment. I took a pregnant test last week it was negative but I think it may be too soon to tell. I have to wait till my next period which is about 2 weeks away to try again. Does anyone know if it is possible to get pregnant without a period? Or am I being paranoid about the situation.