What Causes Delayed Periods With Sore Breasts?

I'm a little worried. I last had sex with my boyfriend on the 18th. He put it in with no condom only 2 times then put on a condom. The previous week, we had sex with no condom, but still only 3 to 4 min and that was it because I didn't feel right with no condom. My period is usually irregular, but the past to months it came was 26 days then I got it. Then the next month it was 27 days and I got it. I was expexting my period yesterday but I haven't got it. I feel tired, my breasts and nipples are sore, I have diarrhea, cramps and I eat a lot of sweets. Am I pregnant, paranoid, or stressed which is causing my period to be late?