Any ideas?

I had unprotected sex about a week or two ago. When I lay down at night I'm feeling nauseous, kinda as if the room is spinning, but I won't throw up. And it only happens when I lay down. I also normally have lots of heavy discharge and I've noticed I haven't had any this week. I'm supposed to start my period tomorrow but have irregular periods anyways. I have not taken a pregnancy test, and may wait a week or so to see if I begin bleeding. Any ideas on what this could be? Any help or advice is greatly appreciated.