It’s really not something you should necessarily ask people their views on, or rather, ask away but don’t take their opinion on the subject.
Medicine mixing is something you’re better off asking your local pharmacist (ie who dispenses your drugs so is aware of what you are prescribed), or your doctor, or even an MS nurse. So I might for eg happily mix certain drugs together, but I might have been on drug number one for some time so my system can cope with the addition of drug number two.
It would seem to me that 10mg of Amitriptyline is a small addition, but I am by no means advocating that you do it. I no longer take Pregabalin so can’t give you a personal view of my experience.