My Vasectomy Reversal

Now that we're pregnant , I've found myself increasingly anxious and fearful.  I started spotting a few days ago.  This is not supposed to be that unusual early in pregnancy, supposedly one third of women will spot in the first trimester.  My doctor has been reassuring, and did an ultrasound on Wednesday.  He was able to see the gestational sack, and encouraged me not to worry unless the bleeding got heavier, turned red, or I started cramping.  Today, it seems heavier and quite red, so we called the doc and went to the hospital.  After an exam and another ultrasound, they sent me home to wait and see.  I'm due back on Monday (a holiday), to see if my HCG levels are rising as they are supposed to.  Right now, I'm vacillating between thinking I'm being paranoid and thinking that I'm right to worry.  

I guess my biggest reason for worry is that if something does go wrong with this pregnancy, what are the odds of it happening again?  Rich's semen analysis results certainly aren't good, so this pregnancy was a bit of a "miracle" anyway.