I can understand you as I suffer most of what you say you have. I am an anxiety patient and just like you say I feel my pulse is weak but never below 60 actually, yet it still seems weak and slow for me. Yesterday I counted my pulse and it was 74, but I would guess 55-60 if I hadn't counted. Actually we feel it's slow because during stress it will go up together with bp and you will feel it all the time. So when you don't feel it, or feel that it is slow and weak, it is actually normal. I also feared it will stop eventually, which it will not. No heart will stop for no reason, it will know when to beat, so if you have your ECG and ECHO clear, meaning there is no abnormality with your heart, nothing bad will happen.
Try not to think about these, because even thinking will earn a place in your head and you will start to have different things - which your mind makes up because you think too much.
For you to relax a bit I can assure you I have or had these things you said:
-Sensation that heart is slow and weak.
-Headache after standing up or sitting down (even with dizziness sometimes).
-Ectopic beats (skippings) most of the time especially after standing up or with little exertion.
-Trying to catch a breath most of the time.
-Fluttering of the heart or other muscle twitches all over my body, different spots every time. But mostly bottom of rib cage.
Even more that I don't remember just now.
Also, like you said when I wore that heart monitor nothing went wrong, the next day I told the doctor "well, i felt nothing yesterday, it's strange". That's what happens when you go to doctor you know that. It's just in your head. You said that as well, you only have anxiety disorder, and that's why you experience these, or make up new ones every other day.
As an ending I would like to tell you my background about these:
First I had irregular beats and started worrying about them last summer. At the end of summer I had a panic attack. Then I kept having both attacks and irregular beats.After about 6 months everything became normal, and about 2 months later I started having funny beats again - WithOut any attack, any rushing of the heart. That's when I started worrying again, but they are still symptoms of anxiety disorder.
Please try to relax and not to think about them. Keep us posted after your other tests and post again if you have anything to ask.
Thanks
