Pregnant?

My boyfriend and I had sex the 15th, which happened to be my first day of ovulation. He didn't cum in me, but we didn't use protection either. I know it's way too early to tell, but the next day I felt different. I was pretty lightheaded and nauseous. This isn't normal for me after sex or while ovulating and I have been worried I could be pregnant. Maybe it's all in my head but I don't know.