During my period of purity, I have yellow discharge that is odorless, and this is the nature of my discharge. However, the problem is that during my menstruation, after the seventh day, I notice yellow discharge. I wait until the tenth day ends and then perform my ritual bath, but I don't feel comfortable because I fear that this yellow discharge is not menstrual blood; it is exactly like my natural discharge. It happened to me that after my last menstruation, I had a period of purity that lasted 12 days, and then I had blood, which I considered to be irregular bleeding until it reached 15 days, and I started to consider it menstruation. However, if I considered the yellow discharge at the end of my last menstruation as my natural discharge, the period of purity would be exactly 15 days, and from the first day I saw blood, it should have been menstruation and not irregular bleeding. What is the ruling?