I had unprotected sex with my boyfriend on April 3rd when we were drunk, he wasn't sure if he came?inside of me or not but I am sure he did. The next morning we got plan b. I usually start my period in the middle of the month, about the 15th or 16th, but I don't feel it coming and I usually do. I've recently started to feel nauseated but I don't know if I should be worried or not, please help