The best thing if you think you might be pregnant, is to not look into your symptoms so much. I just found out last week I'm pregnant and had no signs or symptoms really... My breasts were only the tiniest bit tender... Felt like normal pms just light....
Take a test with FMU and if it's negative, wait and see if your period comes... If not test again or see your doctor. Anything can cause nausea, as said before.. I say don't look so much into symptoms so you don't trick your body into thinking your pregnant if your not.... Good luck!! And let us know what happens.
You do not always experience signs so early in pregnancy, I agree with clysta
Honestly, it could be anything. Illness could cause nausea, it could be stress, it could be pregnancy if you're having unprotected sex or it could be PMS. It might even be nothing. Wait to see if you get your period and if you don't, take a pregnancy test with first morning urine. Symptoms alone don't indicate pregnancy well because so many things can cause them, and you don't actually need them to be pregnant.