Side effects from amitriptyline!?

I've had chronic severe migraines for fourteen years now, and tried different meds which seemed to always cause some kind of side effects. Finally, I was placed on Amitriptyline after about three years of problems with other meds. I thought I had found my miracle cure. Of course I still had migraines, but at least if I could take one soon enough, I could usually just try to sleep it off. Then, about two months ago, I began having what I thought were panic attacks, weakness and pain in my limbs, neck , back and stomach. I also had severe dizziness, nausea and chest pain. I ignored it, blaming it on my migraines and that I became post- menopausal about six months ago. Then the severity of the symptoms increased, until the other day at work, I had to be taken to the ER by ambulance. They couldn't find my pulse until hooking me up to the EKG and my blood pressure was high. My heart was in arrhythmia. I was terrified I was having a heart attack, and could hardly breathe. They ran numerous tests, and it came back my potassium levels were extremely low. They gave me potassium and baby aspirin and told me I was very lucky there was no permanent damage. I didn't take my Amitriptyline the other night before bed and felt better yesterday. Took it last night and am having the same symptoms today even while taking potassium. I think I may have to stop my medicine cold turkey, as I realise my miracle drug may very well be starting to do me in. Has anyone else had this problem with Amitriptyline? I found on the side effects it can dangerously lower potassium, something I didn't know before.