Anyone like this?

Hi all (19M) questioning whether I have IST. I am (mostly) asymptomatic, but I generally have good and bad days and mixed days. Some days I am almost always above 100bpm. Often going up to 120bpm or even 130bpm some days I am more 80-100bpm maybe on occasion dipping into 70s.

I also notice usually afternoon is the best for HR and morning and night are the worst. Morning is worse than night and night can be a wildcard. Some days there isn't a correlation between time and HR.

Some days I am a mixed like 2 days ago I managed to beat my record for lowest and highest recorded resting HR in the same day. Going from as high as 132bpm to 71bpm in the same day.

The problem I have doctors who so far don't take me seriously usually just scape goating ADHD medication and even caffeine. Especially now that hyperthyroidism is ruled out. From what I've seen whether or not I take ADHD medication has almost no effect on HR and same for caffeine. I've been on ADHD meds since age 8 without issue. My BP hasn't changed at all and has been the same for years. My sinus tachycardia was discovered by accident for an ECG for my meds. I still have a morning spike without meds and caffeine.

I am mostly asymptomatic. I did get palpitations when sitting down once and my HR was 130bpm then. When my resting HR is high, I often get mild palpitations when walking. I don't know my HR when walking. I just have a pulse ox.