Hi i just read your post thought id share with you that i also got prescribed amitriptyline by my GP for my headaches too!!
I know what you mean about the drowsiness, although it helped me get a good night sleep at first which i was badly needing! I started off with 10mg which gradually got increased to 50mg a night.
It helped my headaches alot aswell though most of the time. Unfortunately i got taken off it recently though as they were causing me to have a rapid heart rate.
Hope they continue working for you, and you get back to normal soon!
All the best!