Scared and Confused Please Help?

My period has been very regular since the birth of my daughter in 2004, a few hours after she was born I had a tubal ligation. Now here I am 8 days late for my period, I took a home pregnancy test, 3 days ago, it was a weak positive. So I freaked and went to the dr. She did a urine test, it was negative, but then she decided to do a blood test. Blood test was positive, so I'm pregnant. I had a transl ultra sound done and they couldn't find anything yet. I have 3 children already, I'm 25 years old and my husband and I are both college students. We can afford another baby, but if I am pregnant and it is a normal pregnancy, I don't know what to do, my husband is away right now, as he is a MMA no holds barred fighter on the side I am so lost and scared, I just don't know what to do.