Is pregnancy possible???

I'm not on birth control but not actively trying to get pregnant (I'm still a college student and so is my boyfriend) we always use condoms! Last month we had sex during ovulation we usually start out without a condom but never for very long and never ever has he finished without a condom on and we haven't one snap! But this month my "period" came a salad and a half late (that never happens) and it was SO light!! Basically spotting.. only lasted a day instead of a 4(like usual) and it's usually medium to heavy flow... my cramps were out of this world and that's also unusual for me and sore breasts! Please help I think I'm just worked up!