I just need to know if I am allowed to hire someone to do repairs if my landlord won't do them and take it off the rent. Can anyone help?

My landlord refuses to do any and all repairs. I have a broken window boarded up, big holes in my floors and a big hole and crack in my bathroom ceiling due to the people upstairs flooding my bathroom now five times in two months. My fiance has a brain tumor, and the broken window is causing all kinds of loud sounds from the road coming in here and causing near fatal seizures. This is becoming a very serious issue for health reasons here. I need to know if I am legally allowed to hire someone to do repairs and take it off the rent. Yes he knows about this, he has been told and given plenty of warning. It has been a year of nothing. Please..can someone help me?