if it helps to burp maybe it has something to do with your esophogus and acid reflux? Something to ask your doctor about.
"In late October, I had an important soccer tournament where I played through my asthma by using my nebulizer."
Dear lord, why? No, no, no. Naughty soccer play -- if you told your doctor that, he'd punch you in the face. If he doesn't, I would.
I've never heard of asthma relief through burping (I bet that's super hot, btw), so I'm wondering if you're also having an acid reflux-type deal.
Asthma + allergies do go hand-in-hand, albeit not -always-, so get tested if you haven't been or take an over-the-counter allergy med to see if it helps?
You can always talk about different asthma medications if you're still having a tight chest.
And to reitterate a previous point: no playing soccer when you can't breathe. Do it again and I punch you.