An increase in flatulence from the norm (as long as diet is not dramatically altered) means something inside you is creating excess gas:
Especially in the case of smelling unusually horrible, that's a sign of some sort of fucked up bacterial situation:

ToiletDuk said:

Somethings going on in your GI tract.

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ToiletDuk said:

Somethings going on in your GI tract. Cigs will irritate your stomach because the smoke in your mouth fools your stomach into thinking there's food on the way and it starts secreting gastric juices in preparation. When there is none forthcoming, the juices just sit there and irritate the lining. In any case, you might want to see a doc.

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This is about the best answer.. - it might also be a gall stone which is getting stuck in your bile duct, in which case it'll either pass through, or you'll have a pain in your stomach 2nd to none if it gets stuck.

In terms of stomach ulcers - I've been suffering from ulcers for the past 5 years, and in terms of stomach pain, there hardly is any.  First signs of stomach ulcers would be heartburn, excessive belching(burping) and a fairly 'warm and burny' sensation in your stomach.

Other thing to check is your stool color (weird, i know) if they're very dry and/or dark, then most like there's a problem with your gall bladder - but getting it removed is a simple procedure.  Also look out for extreme weight loss and skin and eyes going yellow(jaundice) when it comes to problems with stomach ulcers/cancer and gall bladders..

otherwise man, try eating healthier - specifically try bean soup for a while, and hopefully it passes on by..

btw, stomach pain can also be a result of stress and as said above, not eating properly.

hope that helps man