What to do about AF!

Abby
AF has not shown up since September, no BFP! I have PCOS, I am no my metphormin and prenatuals,plus extra folic aid because our first born was born with a cleft lip and palate. I am not frustrated at it being pregnant I just don't understand why when we are to conceive my periods just stop. 
I am starting to believe it's the stress of wanting to be pregnant and knowing that I am not but still not having AF show up......
What have some of you done to jump start your period? Should I go back to the doctor? I am just really not sure at this point. 
Feeling frustrated. Thanks for reading!