This is tough problem. It could be asthma or allergies or a virus, but it sounds much more like chest breathing. Chest breathing can cause you to breath in and out too fast, which can make you feel lightheaded or at the very least like you can't get enough air.

You need to slow down your breathing when this happens and learn to breath from your stomach (or diaphragm). You can use any technique to work on this meditation, diaphragmatic breathing, or just intentionally slowing down your breath. There are a lot of great videos on youtube you can use. Not to be self-promotional but I have made MP3s for diaphragmatic breathing on my website for exactly this very issue. They're free and you can download them at HOW TO BREATHE DURING A PANIC ATTACK. They're in the middle of the page. Hope this gets under control real soon.

Best of luck,

Jason