Appey - sounds so so similar to what I experienced and as I was cutting down n HRT at the same time I truly don't know which caused it. However the palpitaions and tachycardia started with a bang one evening when I was watching television a few days after having had my second Covid jab. I never felt right since the first one to be honest but the second one floored me - just like you crashing fatigue, awful headache, felt very weak and wobbly, cold sweats, insomnia and the worst anxiety and panic I have ever had in my life. My GP did think it might well have been caused by the vaccine but who knows. This went on for many weeks and 12 weeks really before getting better from it helped by swopping off Oestrogel and going on to Lenzetto. So so sorry you have suffered too. Like you I am incredibly sensitive to drugs and really expected to re-act badly to Lenzetto but thankfully I haven't (well not so far anyway!!) . Do hope you feel better soon xxx