Keto Diet & Period

Hi ladies!! So I recently started doing the Keto Diet about 3 weeks ago and so far everything has been great! However I finished my period July 15th and am not suppose to get it for another 12 more days. But for some odd reason, I have some old blood coming out and I think I’m going to start my period in these next few days. Also, I am on birth control and haven’t finished the pack. Has anyone had this experience!?! Any tips/advice would be great! Thanks!!!