Pregnant?

So I am a 20 year old girl. I have a committed boyfriend. We've been together for a year and a half. Of course we have had sex and the majority of the time we use a condom. Sometimes though we have sex without a condom but he always pulls out. But I have missed my period for two months. I've taken 8 pregnancy tests from the store and they all say not pregnant. I don't feel pregnant.. So does anyone have any suggestions? I plan on going to the doctor and getting a blood test but I don't really want to spend the money...