Stomach Aches

I don't know about you, but my stomach aches quite often.
Things I try to soothe it include tea, milk, rubbing, toilet, and avoiding constipation inducing foods.
Still, sometimes it just remains as it is, and I'm left with the simple task of riding it over.
Another way to allow the stomach to function better (ingestion-wise) is to practice sports. I suspect that my lack of sport-practicing contributes to my ill-feeling.
I keep telling myself I'll do something about it, and of course I keep postponing it again and again.
My self-discipline needs boosting in the way of a coach/trainer. My last trainer closed shop for lack of students (Krav-Maga) and difficulties finding a venue to practice at.
Instead of finding alternative sports, I just let things stay as they are. Bad choice of course.
How does one develop self-discipline if one has lost it so many years ago?
Food for thought.