Cycle day 16 and period is just starting to get heavy

Autumn Kay • ttc since 2014. had a miscarriage 7/2/16.
On CD one - nine is was light and on CD 10 i started metformin and yesterday (cd 15) it started to get pretty heavy. Is metformin supposed to do that? The longest time I've ever bled for was 15 days and now it's day 16 with no signs of slowing down. What do I do. I'm kinda freaking out.