I cant commit,help me out!?

im 36 years old and have always been promiscuous,whenever i get into a relationship i always find ways to make it end.i have been married three times,not one marriage has lasted over twelve months and i have never been the one to propose but i keep saying yes..i dont think ill ever have kids but i desperately want to be a dad..im an average guy with an aveage job..im just average..i sound like dennis leary!do i need help?or am i just "peter pan?"thats what mum calls me!