F/O its a little difficult to be specific about your case, as I'm not privy to the full facts of the matter-your GP / AME is probably the best person to seek advice from.
I can tell you a little about IBS though.
IBS is a colection of symptoms relating to the lower gut, and patients typically describe bloating, flatulence, pain and the feeling that they havn't completely emptied their bowels on defaecation.
As a bucket and spade passenger, I'm often fascinated by those bread role packets expanding as the aircraft climbs- I'm surprised more aircrew don't complain of more problems than they do.
The cause is generally unknown, although some think that an overactivity of the nerves supplying the bowel is a factor. A change in lifestyle (the usual suspects caffeine, fat, ?alcohol, exercise, stress), play a large part. Drugs such as anti spasmodics/anti depressants can help, but in my experience, aren't much use.
About 1 in 5 people suffer from IBS, and it won't affect how long you live-its usually more of a pain in the neck than anything.
Dyspepsia is a symptom ("Difficulty digesting") rather than an illness itself. In some one of your age, I would be hoping that your symptoms would respond to simple lifestyle changes (smoking,alcohol,lose weight, chew your food WELL, and relax after each meal, exercise, stress,) or a short course of simple ant acid medication.
Hope you are now armed with more facts, but as I've said, your AME/GP is key to your recovery.