Hating this medicine! Side effects! Wanting to stop

I have been on 1/2 dose of the ER version (25mg) so I am taking 12.5mg. I have been dealing with post viral dysautonomia after having the flu Dec 29. Having tachycardia and elevated heart rate when doing anything such as standing. I feel pretty weird after taking it until about 4/6pm and then I feel more normal. Feel very drugged. Have been super hungry and cannot seem to get full. My heart has decreased a lot and has slowly creeped back to a more normal. Doctor doesn’t know if it’s my body calming down or the meds working. The past two days I have felt weirder and dizzier and more drugged. I just want to stop this medicine but I am scared for my heart to get worse again :/ Anyone else with these side effects? Anyone quit taking 12.5 and was ok? He also gave me propranolol to try if I wanted to switch