2 periods in 1 month

Morgan

Okay so I have very regular periods. They always come on time and I've never had a problem with my cycles shifting. But this month I have had 2 periods. Glow said i had 9 days until my next period and i started today. It started as a very small amount of brown blood. Then got little pink as it progressed. Now there is small blood clots but still brown or old blood. Has anyone had this happen?