Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Sister, thank you for your question, which shows your desire to live by the rules of Islam and worship Allah correctly. May Allah Almighty help us all adhere to the principles of this true religion, Islam, and enable us to be among the dwellers of Paradise in the hereafter.
What you are experiencing is called istihadah (bleeding outside the normal period). You should stop fasting and salah only for the same number of days you are accustomed to having your menses. After this period you must take a purificatory bath (ghusl) and to resume prayer, fasting, etc.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
The bleeding you are experiencing in this case cannot be considered as menses. It is rather comparable to bleeding of istihadah (abnormal bleeding). Therefore, the rules of hayd (menses) do not apply to your case. Rather you should follow the rules of istihadah.
To be more specific, you are advised to look at the pattern of your menses prior to taking the pills, and simply follow the same. In other words, you simply stay away from prayer, fasting, and Tawaf, etc. (the things you are to avoid while menstruating) the same number of days (i.e., seven days in your case, as you mentioned). After that time you are required to take a complete ghusl (ritual bath) just as you would do when your period completely stops.
Following the ghusl, you must resume prayer, fasts, etc., as if you were totally free of menses. The only exception would be this: You need to clean your private parts and perform wudu’ (ablution) prior to each prayer. You are best advised to perform wudu’ as close to the intended prayer as possible.
Allah Almighty knows best.
Excerpted, with slight modifications, from www.islam.ca