And you could also have something called "walking around pneumonia". Apparently, people don't feel all that bad - just a cold - but can't get a big or complete breath.

I had a student come in for a singing lesson once with that feeling. I made him stop and go directly to a walk-in clinic and they found he had pneumonia. It is easily treatable and can be heard by a doc with a stethascope. But do go and get checked out. There must be 'urgent care' clinics or even the ER if your own GP can't see you. Tuesday is rather far away to find out if you have this.