Am I pregnant????

My boyfriend and I had sex the 17th of February. I got food poisoning the next day so I didn't think much of it but today (22nd) my breasts started to get sore. Is that because I'm pregnant or what? Also my cycles are usually 30-33 days and I'm on day 20. I don't start my next period till the 7th of March. Yes my breats do get sore before my period but it seems a little to soon. I just might be over thinking this too.