A rest HR of 120 is considered tachycardia - and too high, should be treated. It may be related to AFib, but there is no one-to-one diagnosis here. Most tachycardia exists without any accompanying AFib. In my case, I have a high HR due to AFib and I take a Beta Blocker to hold the HR below 100, at rest. My HR is also irregular, a clear sigh of AFib. If in AFib when an EKG is done it is easily diagnosed. Otherwise it may take a wearable monitor for one or more days to catch the error signals/irregularity.
Anxiety and emotional stress of all kinds can cause high HR and irregularity. So, for a starter try to calm down and see if that helps. Being able to calm down is a science in itself... and I struggle with do as I advise on this point.
My doctor always told me that anything even up to 120 bpm could be due to anxiety. (expecially if it fluctuates like yours is doing). Sounds like anxiety to me. Try to relax a little. (easier said than done) The skips are not as prominent because the rate is higher. Stop counting your pulse and buy Dr. Claire Weeks books Peace from Nervous Suffering and Hope and Help for your Nerves. They really helped me.
just telling you my experience...
I went to a different dr who diagnosed me lastweek with PVC, had them for the last 7weeks since finding out my job is gone- but also find stairs VERY hard work - but I can run slowly for over an hour. I find this bizarre and not right!
I kept going to hospital at night with the palpitations - they say 'your stressed pop these metoprolol(betaloc CR) and relax'. I was stressed 6weeks ago but now im fine - yet I still get skipped beats and take one or two 23.75mg metoprolol at night. Now the palps are giving me anxiety!
Just letting you know your not the only one. I have looked up magnesium and potassium and realised I wasnt eating/preparing food correctly too. eg dicing potato instead of baking or boiling WHOLE.
The drs never said diet could help!! So im giving that a go while I wait for 24hour holter monitor test results(2weeks ago)
I didn't know that I should dice potatoes rather than cooking them whole. Thanks for the info.