I’m 15 too and have had 3 periods in a month a few times a few days apart. My mum spoke to my endo about it and he said until i’m about 16 my levels will be a bit all over the place as i’m reaching the point where i’m becoming an adult and until then not to worry about it as a lot of girls without cah have irregular periods too. Like having 1 periods for 6 weeks, so i consider myself quite lucky!