Pre period anxiety

So I had sex with this guy and we are no longer seeing eachother. But in the moment I asked if he had a condom and he said crap no, but trust me... And I'm suppose to start my period soon but when I was getting ready this morning I felt a little nauseous and I'm not sure if it's from my period coming soon, or the other thing....
I also keep having some pain on the left side of my stomach..