Like Natty said, I'm no nutritionist but I can tell you my own experience.
Like others said, it's likely certain foods that are causing this horrible experience for you. I say horrible...for me when I have problems it's downright
painful!
So for me, I finally figured out two BIG culprits:
1. Soy. I scan ingredients lists before I buy anything to make sure it doesn't have soy protein isolate. I stay away from soy milk and tofu, too just to be safe. Major major stomach upset and gas from soy protein isolate.
2. Dairy! I LOVE dairy so much! So when I recently discovered that I was becoming more and more lactose intolerant to the point of severe pain after ingesting dairy, I had a period of mourning.
Once I eliminated dairy, my stomach never felt better. I reaffirmed this last night...I tried to eat some cheese...I was miserable and tooty all last night
.
I'm still in the process of figuring out any digestive problems I may have, but these are the two biggies. Like others said, some people have gluten intolerance, maybe not full blown celiac, but just bad enough to make you miserable. Eating quickly, not chewing your food completely before swallowing (when you don't chew completely, the food particles can be too big for you stomach to break down and this can cause problem with digestion and gas, too), and a sudden increase in fiber can also cause issues. I am terribly guilty of eating too fast! Comes with having 5 sibilings, I guess.
Others mentioned probiotics, that's always a good idea, too. Hope you feel better soon!!!