Sick...pregnant?? Help please.

Okay so I the start of my last period was sept 3. I had sex and he came inside me, fully, (sorry tmi) on sept 13th. My period is supposed to be in two days but I got sick this past Monday. With the stomach flu. I threw up 4 times + diarrhea. And then on wed. I thought I was getting better but its Saturday now and I still feel like shit. I also have no signs of period symptoms except slight cramps maybe. I'm on the pill and I've been taking it constantly for 2 months since I switched from orthotricyclen in July. I did take a plan b pill just in case on the 14th. Can anyone tell me what's going on?? I'm going to wait and test in a few days if I don't get my period. But I'm so nauseous all the time I can't stand it. No one in my house threw up just diarrhea.