I had the same problem after my 2nd child was born. The simple answer is that it could just be that everything is still loose and stretched-out down there. If you practice yoga or anything else where you're getting into a sideways or upside-down kind of position, it can allow air to travel in. When you're upright again, moving around, if you pass gas, it can force some of the air back out and it will feel like you're passing gas through the front. So do kegel exercises often, daily, whenever you remember. That will help strengthen and tighten those loose muscles. This is what I did, and it took me several months of doing this before I finally lost that sensation.
I did also visit an OB dr but I don't think I have enough room to post that all here, so if you'd like to message me I'll be happy to share what I learned with my experience. Good luck!
at 12:31 PM on Oct. 25, 2008