Hi Mushi,
Both of my children had excess gas. It lasted until they were about 10 months. It is horrible and tiring, I know. One thing that helped me through the nights is helping my daughter getting her gas out. I would pump/roll her legs into her belly. When I rolled her legs in I would gently push the sides of my hands into her belly. I would do this as soon as she woke up to feed (sometimes upto 15 rolls) then feed her and then do it again. It was amazing how much gas I got out and then she would sleep quite a bit longer as it was usually the gas that woke her up. Another suggestion is gently circling her stomach clockwise, this helps the air in the intestine get to the large colon, then rolling the legs up into the chest/tummy again. Sounds odd but it really worked for her.
As for foods, he is still pretty young. I would hold off veggies for a bit and stick with the cereals (rice, barley etc) and maybe start the starchy veggies like carrots and sweet potatoes when he is 6 months.
Hope this helps.