All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
You are not obliged to make up the days which you fasted in Ramadan – on the assumption that the shortest possible period of purity is 15 days – and your fasting is correct.
The view that the minimum period of purity is 15 days is the view of the majority of the scholars. The Fiqh Encyclopedia reads: “They (the scholars) differed in opinion regarding the minimum period of purity; the Hanafi School, the Maaliki School - in its preferred opinion - and the Shaafi’i School are of the view that the minimum period of purity between two menses is 15 days and nights, as the month is mostly composed of a period of purity and a period of menstruation. If the maximum period of menses is 15 days, then it is necessary that the minimum period of purity is likewise [i.e. 15 days]...” [End of quote]
For more benefit, please refer to Fataawa 98693 and 91444.
The discharges between two menstruations are not menses. However, if your bleeding continues most of the month and you used to have a regular menses before you started to have continuous bleeding, then you should discontinue prayer and fasting for the length of time your previous monthly periods used to last and afterwards perform Ghusl and fast and pray. This is according to the view of those who give woman's regular monthly period ('Aadah) precedence to woman's distinguishing of blood (Tamyeez): they say that you should not pray or fast during the time of your regular monthly period even if you can distinguish between the blood of menses and other types of bloody discharges. If you did not have a regular monthly period, then you should rely on the distinguishing of blood. Both views are credible and there is no harm in you acting upon either of them.
However, if you cannot distinguish between your monthly menses and other bleeding and you did not have a regular monthly menses, then you should not perform the prayer or fast for six or seven days, and then you should perform Ghusl and pray and fast.
For more benefit, please refer to Fataawa 129256, 192925 and 183343.
Allaah Knows best.