Q: Got my haidh (periods) 4 January after 2 years and made ghusul on the 9 January and started bleeding again 24 January.
A: According to the easiest of the 4 views regarding Tuhr-e-Mutakhallil, the bleeding that reappears before 15 days of purity will be joined to the first bleeding and the woman will consider herself continiously bleeding from the first bleeding. This being the case she will revert to her previous habit of purity and Haidh. Hence if her last Haidh was e.g. 7 days then 7 days from the 4th will be her Haidh and the remainder Istihaazah i.e. after the 11th. Pending on her previous habit of purity and her still bleeding still continuing, her next will Haidh will be calculated accordingly.
And Allah Ta’ala Knows Best