Dont beat yourself up too much about not having any formal lessons. I've been playing for 30 years and never had a lesson. Yes, I've learned from watching others and reading books, etc... For some people, this method works, for others, not. If I had to start over, not knowing a thing about guitar and music, I would have been the first in line to take lessons. Im skilled as a player, yes. But my theory lacks. Thats always been the struggle with me. I can sit down and listen to any tune and play it, but for the life of me, couldnt tell you what key its in. LOL But I do say, that it is fun to learn theory. Im 38 years old, and my mind is still a sponge. I try to learn something new everyday. Its that attitude that keeps music fun for me and not just work.
-Shawn Smith