Could I be pregnant?

So my boyfriend came to visit and we had unprotected sex, I had messed up my birth control on accident about a day after he left. I had like a 3-4 day long period and it was really light after that. But then I missed my regular period and lately my boobs have been sensitive, ive been constipated, bloated, feel just in general sick. Could I still be pregnant even though I had that withdrawal bleeding? I took a test about a week and half after he left and it said negative. Could I still be pregnant??