Lots and lots of GAS!

Not the most pleasant subject, I know. I have found some advice, but not a lot about this. What do you think, especially if you are a distance or open water swimmer? After swimming hard or for more than a mile in the open water, I'm left with the most bloated feeling! I WANT to (let's put it politely) FLATULATE, but just remain bloated for up to 4 hours. I have a feeling this has to do with not exhaling completely, thus compounding the air in my stomach and gut. When I really pay attention to expelling all the air as I swim, I get winded!! I have tried Gas-X after swimming, but it doesn't really work. I just have to wait for the air to "filter out" over time. It can be painful! Do particular foods create gas? Should I hold to the old dictum of never eating less than 2 hours before swimming? Is this something that plagues older swimmers more than young ones? What's going on with me? I'm a 54 year old woman. THANKS!