Are Periods Possible Along With A Pregnancy?

I feel like im pregnant. Had a slight spotting on day 20 of my pill back in october. Then had pil free week, period arrived a few hours later than usual and a bit lighter. changed pill to yasmin, periods arriving clockwork for past 2 months, and heavy(which is normal). But still worried that the origiona spotting was implantation, and the periods were due to the pill hormones. Is it possible to contiue periods and be pregnant? I have had two neg hpt, but have gained 2 inces around waist.