I got the flu a few months ago and developed pneumonia at the same time, and the antibiotics this time around really did a number on my gut. It was a really odd situation.
Anyways, usually gas is something that is not digesting very well, and for me it was every single thing I ate. I started a probiotic (http://amazon.com/dp/B002S1U7RU ) and am now taking it twice a day. But far and away the most helpful thing was I started taking a digestive enzyme (http://amazon.com/dp/B0013OXKHC) before everything I eat, usually 3 or 4 capsules. The enzyme has eliminated about 90% of the "issue". It is amazing stuff.
You should be able to find something very similar at your local health store.
I hope it helps!