Tachycardia

I have been struggling with PVCs and PACs for the past three years and tachycardia . My resting heart rate is 60-75 generally when I am at complete rest. Otherwise it’s in the 80s. When I stand it can go up to 100-190s depending if I am moving or not. The other night I was woken up to my heart racing and it was 170. I could not get it to go down so I did end up going to the ER for some fluids. My blood tests are alway the low but normal reading, but that is normal for me. I have had thyroid issues but nothing that is warrant for medication. They have diagnosed me with inappropriate sinus tachycardia, and possibly POTS. I have been on diltiazem 120mg for the PVCs/PACs . My most recent Holter monitor has said that that my burdens have dropped down to less than 1% for the PVCs and PACs, and now they want me to switch to ivabradine 5mg twice a day for the IST. My cardiologist said that since my burden is low we should focus on the IST. I asked if the burden dropped due to the fact I have been on medication for it and she said it’s unlikely. I have never seen an EP. I am really worried to switch medications. Is there anyone who has these types of arrhythmias? Do you always feel unwell like me?