Running and Exercise Years after Nissen

I'm a keen cyclist and on longer rides I can find that I can become quite bloated (even though I've not really eaten). I have to pay close attention to what fluids and energy gels/bars I use as some can feel like drinking a carbonated drink even though they're not!
One of my riding friends even commented after one ride that I looked like I'd put on weight as my stomach was quite obviously bloated.
I usually find I get pain in the upper abdomen too - as if my stomach is trying to push it's way out of my chest. Fortunately I'm able to burp to expel excess bloating quite easily (which I understand isn't always the case post-op).
I've been largely symptom free otherwise - I had my op around 6yrs ago, which was pretty successful despite a few very uncomfortable episodes with gastroenteritis not long after the op which made me question whether I should have bothered with the op instead of sticking with the meds (30mg Lansaprazole daily).
I'm now starting to get more frequent reflux issues returning, although I haven't really followed a regular sensible post-op Nissens diet (I eat spicy & fatty foods now n then and the odd carbonated drinks) so I guess I'm pretty lucky to have got this far!