Hi,
I experienced pain in the back, neck and left shoulder. That was because I was practicing by sitting on a bed. I bought a chair, started using guitar strap and Foot Pedal and 90% of the pain has just vanished !!

Now for some observations.
1) When I practice with the Classical Guitar Position, my left hand shoulder gets easily tired. Is this because I am so used to the wrong way of practicing that this right way seems..."wrong"....to my hand?

2) When I practice the Chromatic Position, the left hand thumb kind of "creeps" up or down along the back of the neck. So If I'm playing on the sixth string, its slightly above the middle of the neck (but still not peeking out so that it can be seen from the front), and as I start descending down the neck, it sort of "wiggles" down, like a snail wiggling along its path. When I go back from the first string to the sixth, it sort of "wiggles" back. Its I dont think this is right.

3) I have to keep my left hand thumb sideways on the back of the neck to keep my fingers straight. If I place the pad of my left hand thumb at the back of the neck, my fingers, especially the index finger goes in a sort of oblique way.

4) I also noticed that most of the left hand pain is due to my left hand thumb pressing really hard on the back of the neck. So I tried playing with my left hand thumb "away" from the neck so that in time, I will not apply much pressure with the left hand thumb.

Anyone experiencing these issues? Sorry for the barrage of questions, but I would really be thankful if someone could answer.

Please let me know.