Why could i be so nauseas/burping? aug. had unprotected sex and ended up having what seemed liked my period the next day. my period didn't come sept.

Hmm: Check a home pregnancy test. If negative see your doctor for more answers. Good luck

Do a test: Time to do a pregnancy test and/or to have an OBGYN exam. It may not relate to the upset stomach at all - but unprotected sex and a missed period beg the question - are you pregnant? While at the doctor, ask about the nausea. I hope you're okay. Always use protection if you do not want to conceive or get an STD. It's important!