When my mom and dad got married and started TTC she had no luck for over a year! She started to see a fertillity doc and ran all kinds of test and couldn't find a thing! She then told the doc that after all this stuff they have ran out of money and can no longer do testing and see the specialist so he told her wait let me try one last thing! 
He squeezed her boob and milk came out! He told her that because she wants to be pregnant so bad that her body already thinks it is pregnant! So he told her to stop stressing and have fun with it again! And within a month they conceived my older brother! So a word of advice to all women out there TTC like I am, try not to stress or think too much about it (it's hard, trust me I know) your body and mind are very strong and that could be a possibility of why it's hard for some! 
My mom told me a few weeks ago to just squeeze your breast to see and sure enough I did and a tiny little drop of milk came out and now since that day I've been trying not to think about it or put to much pressure! 
Everyone's body is different but I've only heard about this from my mom so I wanted to give my fellow TTC Warriors some advice!