Pregnant After Husband's Vasectomy

My husband had a vasectomy about 16 months ago or so.  He went to all three appointments following his procedure. He called today to verify and both the last 2 appointments showed neg. sperm count.  We just recently started having unprotected sex (this month).  
I am now having pregnancy symptoms (tender, swollen breast, and nausea).  I don't think I'm late at this point, but I'm not positive.  I took a test today, but it was negative.

My question is, what are the chances that his vasectomy could have failed after 2 neg. sperm analysis tests post-vasectomy? Could I be pregnant or is my mind just playing tricks on me?

[amberd5191]

I could just be your thinking, but it does happen sometimes they can reverse themselves...

[AnnieBrooke]

Before you learn whether you are pregnant, send hubby back for another sperm count test.  It will save you a lot of 'splainin' if you are pregs.

[AndiJ78]

Chances are pretty slim if he had 2 tests stating his count was 0. I watched my dh's V, I am 100% certain nothing but divine intervention will undo that. Each Vas Deferens has a knot on the ends, 3/4inch removed and the ends cauterized.

I agree with Annie's suggestion.

[pixijal]

Your not pregnant.