Let down reflex

Patient: My 2nd child is 18 months, and I started weening her at 10 months and was done by 12. I have had my merina IUD in since nov 2010. I got my first period after I quit breast feeding sept 2011, and the past few days I’ve been having several instances of the let down feeling. I was curious of wether it is a sign of early pregnancy or my IUD causing the let down feeling. I have had no other symptoms.