I'm not a native english speaker so I might not find the correct word for a medical condition.
I have cerebral palsy, I swim, but mostly with my hands. My stomach is sensitive, I have high acidity levels, I have Peptic ulcer, when I eat something that can't be digested easily or sometimes when driving for long distances, my stomach turns, I can control it but I still feel it.
I feel the same when swimming due to inhaling and exhaling repeatedly , put the head up the water and in, it shakes my stomach, plus when you don't have oxygen it's worse, and you have less than a second to inhale so it's a fast motion, it's even worse when swimming because you can't stop, take a break until the feeling goes away.
I don't eat anything before swimming and I take Nexium, which is perhaps the defacto medication. I only take it when I want to swim, but it's not helping.
My swimming technique is also immature, I use so much force to go up and breath, I think this is a contributing factor.
Is there some things one can do to make sure that his stomach won't bother him when swimming?