I was banded three years ago and I'm having the same issues as you (except that I haven't been pregnant). I met with my doctor yesterday and she made the following anology. Your band is like a funnel - Water (or any liquid) is equal to oil, if you pour oil down a funnel it will slide right through and your band isn't working right. Sand is equal to the Cs (chips, Cookies, crunchy foods that when crunched turn to sand or powder) and will slide through your band, not making it not work right. Then there is gravel which is equal to eating your Proteins and veggies. Because "gravel" is larger, then your band will be able to work right and slowly funnel through, making you feel fuller and stay full longer. Basically she told me to STOP drinking when I eat and for an hour afterwards!!! I'm a drinker (water, soda, tea) during meals and all it was doing was helping my "gravel" meal slide through my stomach. She said soda is a no no, it creates gas in the lower pouch of the stomach and you cant burp properly causing problems.
This has been tough for me. But today I'm working on turning my bad eating habits into BAND friendly and correct eating habits. It will certainly take some time but I can do and so can you. I've gained about 75/80 pounds back from my original 140 I had lost, and it sucks. I can't deny it, but I'm pretty upset at myself and it's starting to hurt me emotionally. So I've decieded to make the changes that I have to, to be a happier me.