likelihood of dying?

I struggle a lot with thinking my symptoms mean I'm about to suddenly drop down dead, especially in my sleep. I'm working on not being so afraid of death but in the mean time some reasoned stats from knowledgeable people like you lot would help me out a lot.

I'm 19, female and have a BMI fluctuating between 19-21.
My blood tests are all fine.
My blood pressures often near 120/80.
Not sure about cholesterol.
I don't do much excercise atm. Will start soon.
Ecg showed two different types of ectopics.
Echo showed valve on left side of heart doesn't completely close, hence I have a murmer.(In the process of following this up with non-NHS doctors).

Is there any significant risk of me dying anytime soon? I worry about blood clots, heart attacks, strokes etc. Where I don't have much time to realise what's happening, ie cancer.
Is there anything you think I should look out for concerning such things. How bad does something manifest itself when its serious, or can it be serious and silent.
Thank you so much.