Chest infection or just Asthma?

How do you guys normally tell if you have chest infection or if your just having an asthma flare up?

In June my asthma started to flare up and i had to use my rescue more often than normal. They switched me to Advair. The rescue usage decreased but i still have some tightness daily and always have to huff cough to clear my chest..

Now over the last week my breathing has gotten worse the mucus seems like it's a lot worse and i need my rescue almost daily.. while sometimes coughing up yellow stuff. I contact my allergist with these symptoms and she want's me to do the Methacholine Challenge.

Gotta wait for like a month to do this test.... she won't prescribe me anything until i do this... test.. Part of me thinks it could be an infection part of me thinks not... i can't tell!!!

Feeling like crap with no solution for a month.. any advice or experience you have would be great!!