I need advice. BC + pregnancy?

Ok, I normally ask my friends this, but I decided to get the opinon of other women. I'm on orthotri-cyclen (well Trinessa) for about 3 months now. I take the pill everyday, at the same time. About 2 weeks ago, I got diaherrra right after I took the pill. I was still having without a backup. I'm on my inactive week now, and I usually get my period on Thursday, but I haven't gotten it yet. I'm a little worried because usually it comes like clockwork. But last month the date that I got it was the 21st and it's only the 19th. So, should I wait a few days to take a pregnancy test, or should I take one now? I'm not having any signs of pregnancy, other than a little weight gain. And I'm irritated, but not more than normal when I'm getting close to my period.