I honestly don't understand why you would consider putting yourself through more pain/discomfort then you have to. The doctor said ok to take both and frankly, that's what you should do. Most here take the combo.

Your twitching/jerking was here long before the nortriptyline and it's probably just progressing. It's also something the Gabapentin may help with.

You're likely in for a long haul with your plan. Give this some thought.