What are my chances of being pregnant?

i had unprotected on august 8 twice. i've been on and off the pill, but taken it steadily for the past month. what are my chances of being pregnant? i took a pregnancy test 25 DAYS past ovulation (although i didn't use first morning urine, but i've heard that by then hcg would show up in any time of day at this point) and it was negative. i took one a few days before and it was negative, too. but my have been sore lately... and i don't know if it's me being paranoid or what. i was nauseous the other day, but i haven't had anything that i'd consider morning sickness. i feel like there's no way i'm pregnant, but the soreness has me confused.