Could I really be pregnant with my tubes being cut?

I've had my tubes cut or burned after my last baby who is now 3. I've always had regular menstrual cycles however two months ago I went to the bathroom and I bled, but I said how could that be when I had just had a period two week prior, however my normal cycle came on two week later and the cycle lasted for 5 days which is the norm for me. Anyway my period is due now and I'm concerned that It hasent come on yet. I also have mild lower abdominal pain from time to time, which usually indicates that my period is on the way and will surface in a day or so. I went to the hospital to have a simple precedure done and I was tested for pregnancy but the results were of course negative. I just couldnt even imagine that I could be pregnant, when I read the statisics they say the chances of getting pregnant with a burned or cut tubes is like slim to none. Do you think I could be pregnant? Why am I having menstrual like mild abdominal pain but no period?