I have had Generalized Anxiety Disorder for years. In the past I have delt with when I am just about to fall asleep a feeling of falling, and im started awake and my heart beats very fast. It would only happen once and then I would sleep uncomfortably for the rest of the night. I was diagnosed with Fibromaylgia a month ago. I was given Amitryptiline 25 mg and I started on half of a pill for 7 nights. I was amazed at how well it helped me sleep. However the last 2 nights. I have been having the horrible problem where I get the hypnic jerk it will happen 5 times and then Ill be able to fall asleep for the rest of the night. I could deal with the feeling of falling and waking up but my heart beats so fast. I have had had ultra sound, houlter moniter etc on my heart and they say its normal.I dont know if it is the medication, or if its just my own body chemistry because I will get "clusters" of this to happen. I might just be freaking out because I am taking the medication. Thank you