I Went To A Very Dusty Place Once, After Which

I went to a very dusty place once, after which i felt nasal congestion, throat pain, and severe coughs. I went to a doctor and he diagnosed me with asthama and prescribed me medicines. After the visit my condition has just gotten worse, every time i cough my breathing stops. It feels like a granule stuck in my throat which stops me from inhaling, i can't breath at all for a while. I don't know what the problem is, it's not going away , please look into my condition and let me know what's wrong with me. I'm a male, aged 57.