So I Had Sex And Did It With Out A

So i had sex and did it with out a condom , and i was feeling very nauseous and i did not want to eat anything at all . All of a sudden my menstrual came but im still in doubt because it came too early and my cousin said that i can still be pregnant without me knowing yet so i need help in whether to take a pregnancy test or actually go to the doctors and have blood drown out to see if i am