It's not the most natural solution, but Mylicon worked great for ds. He had the same problem. After we gave it to him there was one blast from the front and one from the back. He immediately calmed down, nursed a minute, then went to sleep. We only had to use them twice after that.
You can also try exercising his legs into his belly. Sit on a comfy chair. Place him on your lap with his legs facing you and move his legs gently to his belly. Make sure his knees are bent. This should help relieve some of the pressure. We used to do this all the time as part of a game. Always a tooting good time for us.