I am currently 20 years old. This does not happen with every cycle, but it is happening often. I remember it happening once when i was 15, but has been happening increasingly in the past two years. 

When my period is just about to end, it won't. The blood amount will increase a little bit, then i will continue to have blood for about another week and the amount decreases as the week goes by. The amount of blood is very light, but it gets annoying. Or, sometimes my regular period will end, then a few days later, there will be blood again. The first day will be the heaviest (but its still very light, only need to use a liner), and the amount will decrease throughout the week, or however long it may be. During that time, i will also have mild symptoms of a regular period, like back pain, slight cramps, headache, etc. Its almost like im having about two periods a month, but one is milder than the other.

I did ask a doctor about this, and was told that i dont have any cysts, and that its just an irregular period. But she didnt examine a whole lot though. I keep looking online and not finding anything that exactly matches it. If anything, i could see this being caused by emotional/stress reason because i am dealing with a lot. Does anyone know what it could be or has heard of anything like this?