Hi Alex,
I know -- I had one of those belly buttons that reminded me of those things that pop out when the turkey is ready. We laughed about it. It actually happened with my first, and did not really go down. My doctor suggested waiting until I was finished having children, since whatever was done would likely undo with another pregnancy. By the end of my second preganancy (and last) it was herniated. Since I had a c-section, my doctor just went in and fixed it after the baby was delivered.
I know that you are very concerned about this, but please understand that it is very fixable. Express your concerns with your doctor. Each case is different, and yours may be more simply solved than mine was.
Congratulations on your preganancy -- it's such an exciting time. Here's to a healthy pregnancy - and of course, a healthy child : )