I think that is the problem.
You are empty because your relationship is as empty as void.
Having three partners doesn't equate to fulfillment. In fact, it
blatantly revealed how vulnerable your emotions are to insecurity
and the fear of Love/commitment. People who fear Love often attempt
to gather more partners so as just 'reassure' themselves and acts
as a contingency plan in case one partner 'fails' him. They do not
have to face the situation of a complete lost and could actually
carry on and cling their unhealthy love mindset onto the other
remaining few.
All these relationship you have created are as unstable as MLM. The
minute this grand 'edifice' collapse, you see how weak the
structure of this model is. And an unconscious truth is that: you
are constantly recreating your feared scenario - the fear and lack
of faith towards love commitment:
Fear commitment - create unstable model that it wouldn't last -
realise it is unstable - create MORE of such unstable models -
gradually some fails - recreate more - generate greater fear of
commitment - repeat cycle with greater intensity.
If you call that fulfilling, then you are likely to deceive
yourself through strong delusional reinforcing.
or dun tell mi is mid life crisis already?? or instinct
telling mi to settle down and start a family to share all this
with?.. sighz.....
You have already expressed your greatest fear here
and the novelty of flings is dying for you.
I think it's time for you to mature emotionally. 
Cheers
