I'm working on increasing my vocal range, and I've gotten to G2 as the lowest note that I can sing clearly and loudly. However, for some reason, whenever I try to sing F2, just one pitch lower, it's as though my vocal cords are catching on something, making the tone very unstable and sort of... it's hard to describe. Like a combination of screechy and whiny. I can technically hit the note, but whenever it's stable I can't increase the volume past a whisper, whereas even one pitch higher it's perfectly clear.
Yesterday when I managed to get it perfectly a few times I could feel the difference, so my main question is, what is actually happening? I know the way to fix it - just practice more - but I'm really curious as to why it's like that currently.