What's good for a dodgy stomach!?

I've had a really bad stomach of late, including really bad wind which smells horrible and stomach cramps and a churning stomach, also sometimes have shooting pains coming from my backside if i hold in the toxic odours (cant let them out in most places..)!! I've tried sorting out my diet, eating a lot of salad, not so smelly food although I do drink a few beers on the weekend which I'm going to try to cut out, is there any good remedies that can be recommended? I was thinking liver salts?