All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The longest period which is considered as menses is fifteen days, and the shortest period for ritual purity between two menses is fifteen days, according to the majority of the scholars.
Therefore, if you see blood, then you are menstruating. However, if the total period (of bleeding) when added to the period of purity which happens between the two bleedings exceeds fifteen days, then the days after the fifteenth day are considered Istihaadhah (bleeding outside menses).
Thereafter, if the woman continues to experience Istihaadhah, then she should go back to her regular pattern in menses, and performs Ghusl (ritual bath) after the number of days she usually has menses, and whatever bleeding she has after her regular menses is treated as Istihaadhah.
Since you have a regular menses, as it appears from the question, then you should consider menses only the bleeding you usually experience during your menses, and then perform a Ghusl after that, and consider the period after it as Istihaadhah.
During the period of Istihaadhah, you should pray, fast, touch the Mus-haf (the hardcopy of the Quran) and perform all other acts of worship. All your acts of worship are sound, but you must perform Wudhoo’ (ablution) for every obligatory prayer when its prescribed time starts, and pray the obligatory prayer and all optional prayers with the same Wudhoo’, until the prescribed time of the pray ends.
Allah knows best.