I think I might be pregnant.

I'm afraid I might be pregnant. I'm on the pill but only the second month of it, and honestly I'm not the best at taking it at the exact right time. My period is supposed to start Monday (it's currently Thursday) and it's been 6 days since we had sex. I've been super nauseous but that could totally just be my stomach. And my breasts have been sooo tender, and I've been sleeping like 24/7. We did use a condom, but idk. Am I crazy? And when is the soonest I can take a test that would be correct