Reasons for my missed period?

Stress can cause a missed period, weight gain, and the up and down emotions (which may feel like pms) but since you did have unprotected , it also could be possible that you might be pregnant. The symptoms at the beginning of a pregnancy are very similar to that of a regular menstrual cycle. My advice? Your best bet is to take a pregnancy test. If your two weeks late and you ARE pregnant, there should be no reason that it would come back negative but if it does come back negative, your most likely not pregnant. I would recommend doing the blood test though, it's more accurate than the at home tests.