Welcome to SRP Darren, from a fellow Canadian
It sounds like you didn't have the right angle when you switched to your left hand, and the infirm grip probably didn't help either. I'd recommend taking baby steps when using your left for now - just do small sections until you don't feel comfortable anymore and then switch back to your dominant hand to finish it off. It will become easier with practice, I promise
In the mean time you can practice using your left hand by doing tasks like brushing your teeth. Another popular task is using a butter knife to "pretend" shave.
Keep us posted.