When i sleep on my left side i find i get really bad gas on my right side. when i turn, i can pass it. why?

Easy answer!: Think of a glass of soda--fizz rises to the top, right? This happens with air in your gut. As you see from colon anatomy, there is a left (descending) & right (ascending) part of the colon. Turning onto your left side allows right colon to fill with air (the "bad gas" you're experiencing); turning onto your right side moves gas to left colon which permits easy passage of it thru the rectum nearby.