I do have IBS, but the stomach pain that you describe reminds me of the type of pain I have experienced with the following:
1. Coffee without cream - if I do this a few days in a row.
2. Too much ibuprofen (I have to take something like pepcid 30 minutes before)
3. raw brocolli, green peppers or the skins of cucumbers
4. Any intense prolonged stress
I had it just the other night (woke me up and had it for hours) and I'm not sure why but I think it was from TOO MANY peanuts. The raw foods that do this do it hours after I have eaten them and the pain comes and goes in waves for at least 6 hours (and it's almost unbearable).
With the coffee, ibuprofen and stress--I feel it after eating. My assumption is the lining of my stomach is irritated and putting food gets the acids flowing etc. The first time I had this really bad was after taking Anaprox for cramps for a few days and it just ripped up my stomach. Just a sip of water threw me into great pain.
To answer your question, I don't think you have to have a bowel problem to have IBS but typically people do. I take Donnatal for my IBS, I did take Bentyl at first but I got horrible acid reflux/heartburn (I subsequently read in a book about IBS that it relaxes the valve in your throat--it did for me). In anycase, those medications actually won't touch this pain for me, so I have to be VERY careful about what and how much I eat. Eating too much in a sitting was making my IBS worse for me. Now I eat at least 5 times a day--smaller meals and snacks. Not eating actually induced the pain as I would get gas in my stomach when I got hungry. Bascially, I try not to let myself get too hungry.
The other poster mentioned Celiac disease. That would be something you could try, avoiding the gluten and see if you feel better.
Sorry, I kinda rambled...it's been a long week!