Pregnant?!

Okay so I have had unprotected sex a few times the first weekend of september. 10 or so days after that I bled some. It was lighter than my normal period, less painful and only lasted about 2-3 days and my normal periods last 5 or more and I bleed VERY heavily. Of course I didn't think anything of it. I thought maybe it was just an irregular cycle. My period wasn't actually due til a few days ago. It's 3 days late today. And I feel sick a lot. Not like throwing up sick but it is mild nausea. And I could sleep for days. Literally. I'll sleep for twelve hours and then wake up for two and need another nap. And I'm normally someone who never sleeps at all. Could this be pregnancy?