I don’t think Amitriptyline would be as useful for anxiety as Sertraline. Yes, it can be used as an antidepressant, but the side effects on the dose needed for anxiety would be higher than when used to treat neuropathic pain.
I take Amitriptyline (about 40mg per day) and follow the guidance given to me by my rehab doctor, which is to take it by 8pm in the evening. That way you avoid any ‘hangover’ type side effects. Which is what many people find intolerable with Amitriptyline.
To take the drug as an anti depressant, the dose is a lot higher (about 150mg per day), and I imagine you’d have to be taking it through the day, so you might be zombified by it!
You could ask your GP whether you can take both Sertraline and Amitriptyline. You may well be able to replace the Zopiclone with Amitriptyline. (Although I take both.)
Amitriptyline is very good for burny/itchy/sharp pain. That’s what I take it for. You could also ask about Baclofen for spasms. Which probably wouldn’t have a sedating side effect, although some people do suffer weakness. The problem is that you need your muscles to have some ‘tone’ and tightness, so if you find you reduce spasms but in the process make your muscles too weak to work properly, you’d be exchanging one problem for something worse.
I take in a combination of Amitriptyline, Baclofen, Cloneazepam and Zopiclone. I just have days or weeks off the Zopiclone so I don’t develop a tolerance to it.
I should just talk to your GP about your symptoms and ask what they think about the various drugs you take now and what can be added to or replaced in order to achieve the results you want.