concerned about my age

Christi
I am thirty-one years old and we have been trying for a baby number 3 for about three months now.  I have never had a problem at getting pregnant. Usually it's like a bam I'm prego first try kinda girl.  FERTIAL  MERTLE       BUT  holy it seems like it is taking a lot longer which makes me concerned maybe I'm already a dried up prune.   My second child is four so it's been awhile since my last child.  Any thoughts on why it may be taking a lot longer this time? And of course to me 3 months seems like an eternity lol just because it doesn't take this long normally for me.