I'm experiencing tightness in my chest and it's becoming hard to breathe. I've been diagnosed with allergic bronchitis and usually use my asthalin inhaler, but it's not providing much relief this time. My nose feels sort of blocked, though I don't have any other symptoms like a cough or cold. I've tried taking Allegra too, but the tightness in my chest just won't go away. What could be going on?