Been having spasm sense i woke up

[Johnnie1234]

I could feel spasm on my ribs and on my chest right side and left side by my heart idk i feel like something is wrong with my body i could be laying down feel spasms and feeling shaky my hands aswell . im on metaprolol i took it two days go when my heart was going really fast the cardiologist told me i had a little bit if arrythmia but not a dangerous one he didnt give me metaprolol In the ER they did because they say my heart was really high and refer me to see a cardiologist but he says im fine thats why i stop taking them and only take it when i really need it but its say take one tablet twice a day i dodnt take it like that i only take when i need it but mostly everyday i get them but i try to control it . idk what she i do with the metaprolol eather if i should follow how it says to take it or take how i take onky when i feel my heart rate going really fast but my question is idk if its dangerous taking them Off and On.