Huge hypohondria episode...

I'm 18 years old. I have always been a slight Hypohondriac but after a death of a close relative things have gotten out of hand.

I always keep thinking that something is wrong with me, one day my lungs aren't functioning properly, the other day i'm thinking that my heart isn't working properly.
Even though i know i'm perfectly healthy and fine, deep down i have a feeling like a have some sort of disease. If my relative didn't die of such a disease (cancer) none of this would have happened, which is a dumb reason.

I have trouble sleeping at night because i always think that my heart will stop beating and i'm going to die in my sleep, even when the chances of that are 0%.

The thing that bothers me now is that my resting heart rate is 54. I'm not athletic, my weight is 74 kilos, i'm 194cm tall.. I'm a lazy - slim looking teen.
Could that be normal? Even when i'm laying down and i stand up to go for something my heart rate jumps to 80-90bpm. I played badminton a few weeks ago and i inflammed my intercostal muscles, so i always had this annoying "pressure like" feeling in my chest, like i couldn't breathe.

I'm healthy, my blood pressure is pefect and i'm feeling absolutely fine day to day, i don't get dizzy when cycling or walking and i can do normal tasks just fine. Is my heart okay, or am i having the hugest hypohondriac attack yet?

FYI, heart disease doesn't run in the family.