A faint positive is still true?????

I have been having with my bf of 9 months pretty regularly but am on the pill. We both got tested before we did anything and for the most part have used a condom.I am 19 and he is 34 years old and has a 10 year old daughter already from the past. The year before we met he had a vasectomy done the thing is i have not had my period in two months?At this point we dont really use a condom and i do miss a pill here and there can i be pregnant?even though he has had a vasectomy? I took tests both with faint positives?