No problems Nick, boxing is by far the most physically difficult training regime about & I would suggest trying it out without involving yourself in sparring.

Go to a boxing gym & explain your situation & they won't risk doing anything bad for you. See how the physical workout goes for you. However, you will get hit in the stomach at some point, it's just a fact. If you don't keep your hands up you'll get your chin caught. Most people learn to take shots to the body with extensive conditioning, which with your condition of your stomach may be a problem.

If you're looking for a martial art that involves less hitting to the stomach, I'd try kickboxing & jujitsu talking from personal experience. However, in almost any martial art you will probably take a hit to you gut sooner or later. I definitely recommend giving boxing training a try, but if you do find it a bit much those other two are good alternatives. Also for a less aggressive choice, capoeira is a good option.