How bad is the weight gain from Nortriptyline

I want to try Nortriptyline for my Atypical face pain, which I believe in my case could be chronic migraines. For those who have been on nortriptyline, how bad was the weight gain if any? I have pretty good eating habits and certainly would watch my food consumption, but does it actually make you gain weight without even eating more?

I would type the med in

Or ask pharmacist