Sugar might be a big contributor to your palpitations, high heartrate and low weight.
I used to eat TRUCK LOADS of sugar until recently, and i'm also very skinny.
For some people sugar doesn't make them fat, and can actually make them SKINNY!
I suspect sugar can eat away the muscles and important mineral such as magnesium.
You don't need to be on a completely carbohydrate-less diet, just avoid refined sugar at all cost and don't eat too much carbs.
joseph goldstein has a book on vipassana.
Thank you for responding to my post. Most of your guess is right. I have already stopped taking weed. But I don't have any disease. The reason why I am skinny is improper habit of eating, & I kind of like sugar with tea, coffee or anything sweet. I will change it. My kidneys are strong, cause I drink a lot of water per day. I want to know more about vipassana meditation. In our country I wont find it. So please tell me how to learn about in home.
you are "5 feet 11 inch = 180.34 centimeters " and weigh only 52 kgs? you are way too skinny.
stop the weed immediately, cut down on the cigs if you're smoking a lot of them.
if you're body is too weak for sports then sports might work against you.
do you eat properly?
you should get your blood checked by a doctor to see if you have a disease that is causing you to be so skinny.
if you don't have any disease, then you probably don't eat enough protein or eat too much sugar. sugar can eat away the muscles and cause people to be skinny.
once your body has become a bit stronger u might be able to do a little sports.
dont try to be too active too quickly, your body might need some time to become strong enough for a bit of activity.
you're heart is probably healthy, but you should possibly get it checked out anyway just in case.
if you've had poor nutrition then you might be low in magnesium levels, even when the bloodtest says you aren't.
in that case you could try to take magnesium as a supplement (i think people with weak kidneys can't take magnesium so be careful!)
magnesium helps a lot of people to get rid of their palpitations,
but unfortunately it does not do the trick for everybody.
don't smoke weed anymore, it is bad for the body and heart (i learned the hard way)
and if you want to get high try something natural like dancing to music or doing meditation. (i recommend vipassana meditation)