Cardiophobia

So a short story of mine. Two weeks ago i got my vaccine and i was so stressed about getting myocarditis that i have several panic attacks. I been to a cardiologist and he told me i am fine. Since then i keep checking my heart rate and i realized that i have developed POTS. Here is were my anxiety starts all day i keep checking my heart rate. When i stand up when i sit, when i eat and when i drive. All day my rest heart rate is high due to POTS i believe and during night my heart rate come back to normal around 45-50 were it used to be. Every night i fight with demons because i think my heart will stop working while i sleep. I booked an appointment for other cardiologist so he can see my heart and tell him that i might have pots.(just i wanna hear my heart is fine and i wont die). I never had anxiety but since my vaccine i am close to depression i was working out 5 times per week and a marathon runner since i realized my heart rate going up just from standing up(Pots) i stopped everything. I am afraid to go out, i am afraid to eat so my heart has all the blood, i dont talk to anybody and i am just laying on bed. I dont study for my exams and i gave up life fearing that my heart isnt working well. I dont know what to do someone help me. I think i am a broken man.