Pregnant or Side Effect?

I’ve taken birth control pill every day for over a year, always on time. About a month ago, I let my boyfriend ejaculate in me for the first time (because of scares like this). It was right before I started my period that month. I bled just like normal the whole week. Now about 2 weeks ago I started an antidepressant called bupropion (Wellbutrin). I should be on my period now, but I only bled barely ONE day, the first day of my period. Now there is nothing. I looked around on the internet and some women have experienced irregularities while taking this med. I’ve had symptoms of pregnancy but they are also side effects of the med. I haven’t taken any tests yet. Please give me some input! How likely is it that I’m pregnant?