Welcome to SR!!
I agree with the others - do please talk to your doctor and just tell him/her what you've told us, especially that the cravings increase when you are pregnant.
I did a little research and it seems that many women crave this when they are pregnant and it can be related to iron.
I used to be a nurse, lost that career to addiction. I learned, however, that a doctor can't help you if they don't know all the details. Though reaching out for help seems hard, it's actually a sign of strength.
Hugs and prayers,
Amy