I think we all sort of feel this, but we all think we are the only ones. Michael Harding has written a book about the emptiness we all feel in our lives, it's an autobiographic book titled "Staring at lakes". He also writes something in there about how to deal with it, or come to terms with it. Maybe reading that book is a start.

Someone also posted a sad, but wonderful poem about it, can't remember which user! But here it is.

"no help for that"

there is a place in the heart that
will never be filled

a space

and even during the
best moments
and
the greatest
times

we will know it

we will know it
more than
ever

there is a place in the heart that
will never be filled
and

we will wait
and
wait

in that space.”
— Charles Bukowski

You're not alone!

EDIT: Found it. The user was Velouria, and the thread was here. Seems to be about the same as you are dealing with.