How much longer do I have to wait?!?

Stacie • Mother to Ben 👦, Bash 👦, and due with Baby #3 March 2018, 420 enthusiast 🍁🔥💨, lover of life 😍✌
Ugh! I've been trying for 14 months with nothing to show for it... I'm super impatient! 
​My question... Why do some women try and try but don't get pregnant for a long time and other women don't try at all and get pregnant the first time?
​I'm just a 19 year old trying to make a family with my husband. He doesn't want to give up but I'm slowly losing hope for myself...
​Any advice for me?