3 days late with sore breasts and nausea

my boyfriend and i only had sex a few times this month, about 3 and everytime we do we use a condom, he always pulls out and then we always check to see that it hasnt broken. i started going to the gym 3-4 times a week this month and i havent done excersise for ages, i also had a cold this month, and now i am really stressed out. My breasts are sore and hard, and im really moody, but that happens when i usually get my period. i also started feeling like i was going to throw up last night and this morning, but its kind of gone away now. that stressed me out more, but i might of been making myself sick, what do you think??
can someone please help me? am i pregnant? what are the chances of being pregnant?