1) I know that the heart has to beat faster when you stand up. Could it be that for some reason I am more sensitive to these heartbeats than other people?
A: You are correct that the heart rate rises when one stands. This prevents people from passing out everytime they stand up. You are also correct in your observation that some people notice changes in their heart rate more than other. Why this is no one really knows. I would love to hear any theories from people out there.
2) My normal resting heart rate is between 64-80 but sometimes my heart rate will be in the nintees and stay up there for 2-3 days and then returns to normal. Why does this happen? Is it normal?
A: It's probably normal. Do you do any cardiovascular exercise? If not I would establish this as a regular routine. It will help lower your heart rate and help you feel better overall. It is possible (but unlikely)that you have some form of low grade inappropriate sinus tachycardia and you can read more about that condition in other postings on this site.
I am a 20 y/o female, that often experience heart papilations. I have a heart murmur and a slight leaky valve, the doctor couldn't find out what it was caused from she just said I am extremely sensitive. Most people have what I have and do not feel their heart fluttering or skipping beats but I do because I am extremely sensitive.