Using Flexeril for your headaches is a completely different approach from using amitriptyline. Flexeril approaches things from a muscular direction, as opposed to vascular(?) in the amitriptyline. The Flexeril can really knock you on your ass until your body gets use to it. Unfortunately, you can't use it continuously, as you will get use to it. I took it for a long time, and now I could down half a bottle without feeling a thing. I never had any success with the amitriptyline either, and you really have to watch what side effect you get immediately from the start. I was on Depakote for eight months and it gave me really bad eating disorders. I would pick one food, like Kettle Korn, and eat nothing but that for a couple of months. However, I was going through a box a day, and I ended up gaining about 80 lbs. in about 8 months. The medication also gave me dry mouth, which nobody told me would turn into massive cavities (about $4000).
What you might want to do is lower your dosage of Flexeril, and add short theraputic massages. Massages do a world of good. I just had a full body massage done in the Health & Rehabilitation Center at the local YMCA, and it was cheaper than medication and felt a lot better.
Jest my two cents worth,