Is my heart rate too fast?

[ruben_3301]

I'm 17 years old seemingly healthy. I've been to a few cardiologists who told me I was fine but that is hard to believe when my heart rate exceeds 200bpm just by walking a few blocks. My weight is perfect, I eat healthy, I keep myself hydrated, and I am not that sedentary since I walk every day and according to my phone, I do about 7,000 steps per day.

This has kept me so anxious that I feel stuck, my doctor doesn't believe me when I say what my bpm has been. I walk to the bus stop and as soon as I stop walking, I can feel my heart pounding in my chest. When I take my HR, it is usually about 195bpm but sometimes about 204bpm. When I walk up the stairs, the same thing. I'm even scared of exercising.

The only thing that is keeping me from freaking out is that I don't feel pain when it is happening and that don't get dizzy.

Appart from that, I get a headache when it happens, I get slightly out of breath, I feel my heart's blood flow like I can almost feel the blood going through my chest, and if I exercise, I will get ectopics. My heart stops... and then keeps beating again. Sometimes it will get all crazy and jump around for like 2 seconds and go back to the super high HR I was having previously. Oh, and the crazy fast heart rate is regular as far as I can tell.