Ryan...
I, too had my first child 3 months early. And my second child was born healthy and only 3 weeks early--which is still in the realm of "normal".
Get the information from your Lap Band doctor about how the band works with pregnancy--in my preparations they did a whole section of information about this--DON'T let it cause you this much grief.
Talk to your OB--if you don't already KNOW, find out WHY your first child came early. They should be able to put your mind at ease about your new child and hopefully take steps to provide for a safe and full-term pregnancy. I'm curious, if you are wiling/able to share, how is your firstborn's health now?
REJOICE--while you're creating this new life of your child, you'll also be reclaiming your own life.
I am SO excited for you--