Hi Jo girl
So sorry to hear you've had such a frightening time of it in menopause, but sadly you are not alone in this. Have a good look around the forum & you'll find threads on anxiety with advice about coping. Many of us can relate to the small hours & early morning being the worst time for these feelings, but as you go further into postmenopause the body does stabilise to some extent & many women find things do get better.
As for palpitations, I had episodes of irregular beats lasting an hour or more on & off day & night for several years, starting in perimenopause & continuing well into post-menopause. I agree, they can be very unnerving, not to say downright frightening & at first I found it hard to believe the heart could be affected by gynae hormone disruption, but it certainly can. They are fairly common in menopause & there are a number of previous threads on the forum discussing palpitations that might give you some reassurance - you could maybe use the search facility & enter something like palpitations, ectopics, or irregular heartbeats.
As you know, thyroid conditions can also be a cause, as can anaemia. I'm not sure how recently your thyroid function was tested, whether that included antibodies & whether anaemia was ruled out, but if you have symptoms suggestive of either I would go back to your GP & ask for further tests. Likewise if you feel your palpitations need checking out again with cardiac tests, if only for reassurance. Beta blockers help some women with palps & your GP may feel a trial of these worthwhile if you are willing.
I'm long term hypothyroid & my palps were investigated by ECG, treadmill test, echocardiogram (ultrasound) & 24 hr Holter monitor & found to be harmless ectopics & this is the case for many women. They finally stopped around 3 years post-meno, shortly after starting systemic HRT, coinciding with a change to thyroid meds. Subsequent changes in HRT regimen have caused them to return briefly, sometimes with a vengeance (Utogestan is a no-no for me in this respect) so gynae hormone depletion/fluctuations/imbalance seem to be the cause for me, though thyroid disease certainly muddies the picture at menopause. Changes to my thyroid medication dose up or down usually also cause a return of palps but only for a few weeks & this then settles.
Several years after my ectopics had started, a gynae who had previously worked in Cardiology told me many women had presented at the clinic with palpitations & after extensive investigation no abnormality could be found - but they were all of menopausal age. I hope this is a little reassuring - I wished I'd known it years earlier, as they can be a source of considerable anxiety, so I do feel for you.
I wonder whether you want to consider a retrial of HRT now that you are at a different stage of the transition, to see whether this gets rid of the palps & helps you feel better generally. It need not be long term - sometimes the body just needs a long enough break to recover & HRT can provide the stability that enables this. Slowly weaning off afterwards is sensible to safeguard against the body plunging back into full on panic mode.
If you haven't tried meditation I can vouch for the efficacy of this in calming the whole body over time & there are many studies showing its wide ranging health benefits. Controlled breathing during anxiety attacks & to reset the palps can also be helpful, but you may need to do this for a good few minutes at a time - I found around 20 mins was necessary but that's not always practical depending on situation. It can be a calming exercise when awake & anxious in the early hours, feeling like the only person not asleep - the boredom of repetition may also help you get back to sleep! As CLKD says, rest & relaxation of all sorts can help - whatever floats your boat - so do try to get as much as you can.
Oh, should just say that caffeine & alcohol can also cause palpitations.
Whatever you decide to try you're certainly not alone, nor going mad & you will find lots of support, advice & wisdom here. I do hope you find something that helps you feel better soon. Keep posting.
W