Since you are working towards becoming a vegetarian, you probably are eating a lot of vegetables and fruits. Are you eating a lot of beans, such as kidney, pinto, cannelli, etc? Beans are know to produce lots of gas.
There is a great article about gas on the National Digestive Diseases Information Clearhouse. http://digestive.niddk.nih.gov/ddiseases/pubs/gas/
I bet if you read this article you might find the foods causing your problem.