Really freaked out that I might be pregnant

I'm 18 and have been sexually active with my boyfriend only for the last 1 1/2 years. We use a combo of condoms and the pull out method together (meaning he always wears a condom but also pulls out). We probably have sex 1-3 times a week and I've never noticed any condom breakage or rips and they've never fallen off. I'm on day 29 of my cycle, which can range from 26-31 days. I have 2 days to get my period before I get really worried. For the past week or so I've been having some kind of strange discharge (white) and I've been nauseous and anxious. For the past two days I've had period cramps and woke up in the mornings 100% sure I had gotten my period (I always have a very specific feeling when I wake up with it) but nothing. I don't know if this is all just from stress or not. Help?!