When you say your left arm is at a right angle - do you mean that your left elbow makes a right angle, and with respect to what plane in space? If that's not what you mean, what is your left arm making a right angle with?
I had all kinds of problems when I started playing. I'm tall, and I didn't fit with any of the guitars I tried. If you look at my avatar, you'll see a perfect example of how
not to hold your right arm. The elbow is sticking out from my body, the elbow is angled far away from the vertical plane, and it was flat out uncomfortable. I also sometimes contorted my left arm, depending on where I was playing on the neck. My defense is that I hadn't been playing long, there was nobody anywhere near me to show me how to do it correctly, and the steel (and every steel I had played up to that point) wasn't set up for me. It was too low, I had to contort myself to get my legs under the guitar, I was addressing the guitar all wrong, and it was very uncomfortable and aggravated my elbows and my lower back.
I ultimately figured out that I had to raise my guitars with a lift kit and learn to address the guitar in a much more relaxed and comfortable way. It is generally considered proper form to tuck in your elbows in and address the steel in a relaxed way, with the elbow making its angle at or close to the vertical plane. When when I started doing that, my problems got a lot better. To get there, I had to work to figure out the proper height for the guitar and the seat, and where to sit relative to the guitar. I look at videos like this (of Buddy Emmons) to get a sense of how I need to address the steel - the way he addresses the guitar looks totally relaxed and natural:
https://www.youtube.com/watch?v=55W8kMDm6_w or
https://www.youtube.com/watch?v=tFuYmuZpFiw
Anyway - that's where I'd start - looking at my form. It does not have to hurt to play pedal steel guitar. Put your steel in front of a mirror and see what's really going on. I also found a week working with Mike Sweeney did wonders. A good teacher can probably diagnose any ergonomic problems pretty quickly.