I also draw stuff facing left and I'm right handed but I think it's more of a habit. I drag my hand on the surface of the paper when I draw so when drawing something facing right, I feel like I'm going backwards when my hand is dragging on top of the characters face. Just need to sketch more fluidly and try not to smudge the drawing with dragging. Just takes a lot of practice to learn how to draw stuff facing right.
I'm left-handed, and I always paint with the light source coming from the right, so I'm 99% sure it has nothing to do with handed-ness. It's just habit, usually; it can also be a side-effect of culture. For example, in most languages, we read from left-to-right and top-to-bottom, so it makes more sense for us to draw characters at the left side of the page facing towards the right. It also makes sense for the light source to be opposite, as well, if they're facing in that direction. Just try to practice odder lighting schemes, and moving your focal points around (placing the character on the right, putting the focus on the lower-left, different stuff like that). If you're working digitally, you can also start normally, then flip your image from left-to-right and finish it up in that direction. It's also a good habit to flip your work as you're going anyway, since it'll let you catch errors you might not have seen otherwise.
The other benefit of flipping your own work is that it forces your brain to see it as a new image, so sometimes anatomy errors, etc will become more obvious (when you're working on something for a long while, your mind adjusts to compensate for any errors it sees, so you can end up thinking everything's all perfect).
Yeah that's another thing I was thinking... I might be able to find out why I can only seem to draw things one way. It would be of great assistance to my cause... That being a want for greater progress.
This happens to me too, I think it's because I'm right handed. It can be difficult sometimes to catch myself in the act, because drawing the lighting , and scenes that way has become a habit over the years. I still have a lot to work on in correcting it, but I like to think I'm getting better at it. As for your second question about the photos, I can't really answer that. I don't have much experience when it comes to photography.