My menstrual cycle has changed. It use to last for five or six days. Now, on the fourth day, the bleeding stops and I start bleeding again on the fifth day. When should I do my ghusl? Shall I do it on the fourth day or wait till everything is finished (thus ignoring that the bleeding has stopped on the fourth day)? Jazakallahu khayran.
You wait until you see the Tuhr sign, the purification sign. This sign is either a white liquid or a complete dryness. A dryness can occur in the middle of the cycle, so you consider this day from the menstrual period as well, and you make ghusl after everything is finished. This is the fatwa of Shaikh Ibn al- Uthaymeen.