2 years ago I had polycystic Ovary. I took medicine and eco shows that im ok. Then everymonth my period is 2days earlier. This month it's 5days early why?

It maybe just a fluk. However watch the pattern.You maybe developing a menstrual problem again.
Normal variation. If you mean that every month your period comes 2 calendar days earlier that simply means your cycle is 28-29 days in length. Only those with 30-31 day cycles have periods the same day every month and even birth control pills won't give you this. There is some normal variation in cycle length because not all eggs mature at the same rate anymore than all children do. Hope this helps.