salamou aleikom,
it has been a year now since i found out that my father is betraying my mother. i probably shouldn't tell her so i won't interfere in their marriage and i probably shouldn't confront him, i don't know what to do, it's such a heavy burden, i'm falling apart everytime i see him with this other woman, i feel sad for my mother who's working hard everyday and trying her best to satisfie everyone of us in this family, i get so angry everytime i see her trying to make him happy and pleased, she even sacrifices her own needs just to let us get ours, she's the best mother and wife. i don't why he treats her this way and i can't take it anymore. i'm sad i'm tired and i really want this situation to end. what does Islam think i should do? should i tell? if not, what should i do to feel better?
jazakom allah kola khayr

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 is His slave and Messenger.

What you should do is to hasten to advise your father and remind him of Allaah as well as that what he does incurs the Wrath and Anger of Allaah. Then, if he takes heed, you should conceal the matter from your mother and from anyone else. However, if he persists on what he does and does not take heed of your advice, then you should inform someone about the matter whom you think may deter him. If your mother can do so, then it is permissible for you to inform her, otherwise you should conceal the matter from her and supplicate Allaah as much as possible to guide him and enable him to do good.

For more benefit, please refer to Fatwa 92195.

Allaah Knows best.