Nipple discharge

I've been pregnant twice and lost my babies both times. 1st pregnancy I was 9weeks (4years ago) and second I was 12 weeks (April 2017)each time I would have some nipple discharge like milk or something. 2 days ago my boyfriend was sucking my nipples and he said he tasted something. I didn't believe him until my nipples started to leak and when I pressed them that same milk like discharge came out. And I'm not pregnant because I just ovulated last week. And my period is due sometime next week. What could this be?