is it possible to get pregnant while using condoms?

My boyfriend and I had sex Sunday and we used a condom. I've started to feel really weird. My stomach feels bloated. My boobs are really sore. I have cramps and I feel more emotional than usual. It feels like my period is about to happen, but it isn't due until around the 20th. The condom didn't break and we didn't have sex without one. It did try to come off a little, but it didn't come off completely. I'm going to get a pregnancy test tomorrow and see just in case. Could this all just be in my head?