Could I be pregnant?

My boyfriend and I had sex the weekend of the 23rd and we didn't use protection and after we finished he mumbled something about it being a small load so immediately I was scared that he partially came in me but I didn't say anything. I just had my period last week and it was lighter than usual and ended a day early. I have been nauseous during the afternoons for at least the past week if not since the end of last week. I have also been finding myself much more tired than usual. I've been going to bed at 8 pm every night and I'm usually an 11:00 kind of gal. I have also been getting like mini cramps in my ovries, not sure if that means anything. Even laying in bed right now I am nauseous. Is there a chance I could be pregnant? My boss said she got her period when she was early in her pregnancy with her daughter.