You might also want to check your elbows when you are mid-way into a ride. See if you fall into a "locked elbow" posture as your arm muscles begin to fatigue. Keeping those elbows soft uses a lot of muscle power, but it's very important (especially with a history of arm injury) to keep the elbows soft.

Bike fit influences everything, so I second the get a fit recc. You could also do some research before your fit with Andy Pruitt's book: Complete Medical Guide for Cyclists. Someone here on the board pointed me to this book, and it really is a great book and the writing is clear and easy to follow.

And welcome to TE!