Hi,
I suggest you go to your local dog educator to learn a new leash style. I have no strength in my right arm at all so at first my puppy was a puller and he pulled like hell for me!!!!!!

I went to puppy school which is awesome if you have not been. They understood my issues and showed me a way to harness the dog with a long leash so that I had total control with my left arm and he could not pull on me.

It is so difficult for me to describe what i did to the dogs leash
It was a hard time for me to remember.....but (don't go by these instructions get proper help!!) you loop the leash around the collar so that you have a loop on the left side of you and a straight bit on the right. It stops the dog from pulling because the strap goes over his/her chest and keeps him at pace with you so no pulling or sore wrists or arms. I can now walk him loose leash with the command of heel and he soooo gets it.

I don't know if this helps but if you try emailing the girl I learned it from it may help.
her email is friends4life@shaw.ca her name is Tina Sarantis. Ask her in the email to let you know the leash technique if she can that she taught Marc Victoria and Charlie last spring. We took her class at positively pooched in Calgary.
anyhow she is an amazing woman and i'm sure would be glad to help you out if she can. Remind her that I had right arm pain and could not hold the leash well to walk Charlie because of his pulling I think she'd remember us.
We are going back in the fall to her and she knows that.

I hope some of this helps you
take care,
Victoria

ps I have emailed her to let her know that you may email her so she has the heads up and is not left wondering what's going on! good luck. Vic