preg symptoms

Hi all! My husband and I have been trying to conceive for almost a year now. Last month I started metformin due to diagnoses of PcOS. I am 3 days late as of right now, my boobs are sore as they normally are around my period but  starting today I started having a milky discharge that I've never had before. Not sure if this is a side effect of the medication or a pre preganancy symptom.  Of course I'm hoping for  a positive test in the next few days but I'm scared to get my hopes up.  Is this normal?