K.B.
I really wouldn't worry too much that he isn't sitting up. My 10 month old didn't start sitting up or crawling until she was 8 months old. I talked to her doctor and he just said that every baby has their own schedule. As for the gassiness, it might be too much food. My daughter is the same way. She can chow down on food when she wants to. I try to slow her down and give her either apple juice or something else to drink in between foods and that seems to help.