Is it normal & natural that a parents worsts fear is their own child dieing?

My son will be turning 2yrs old on the 27th of next month (April) & ever since he was born i always worry sick about him i love him more than life he is the air that i breathe he is my world, he is my only child & i just love him more than you can imagine but i always worry about him i worry that when he goes to sleep at night he isnt going to wake up the next day or that he is going to die during his sleep? The other day he was playing out the back & i went out their to check on him (i only went inside for a few minutes) but when i went out side i looked all around the back yard for him & i couldnt find him & my heart started beating & i felt like crying but then i found him hiding in the washing basket & then when i found him he was laughing cause he hid from me lol! But thats my worst fear my child dieing he is so so sooo cute he is so loveable he is perfect & his name is ''Matthew'' is it normal that im worrying all the time for him? when he gets babysat i always ring up aswell.