Difficulties singing louder, vocal fatigue
I've been singing in rock bands, including gigging and recording, for quite a long time. Recently I've had several colds, which haven't helped my singing voice.
I've noticed a lot of vocal fatigue. Last weekend I stayed up with someone and had 2 drinks after singing and the next day I was feeling pretty hoarse speaking. However, I can sing everything quietly quite comfortably, with virtually no hoarseness. It's when I start to add volume, particularly around the g#4-d5, that I get problems, with the sound coming out very inconsistently, sometimes for a few days after a (not very heavy) night out. I'm giving up on alcohol but I'm worried about there being something bad going wrong with my voice. At the moment, that part of my range is still not great, but I have zero speaking hoarseness or hoarseness when singing quietly, just a fair bit of phlegm.
What exactly is going on here?