landlord neglect

We have been renting our home for over 2 years now, and the roof started leaking last year. Now where the roof is leaking the walls are covered in black mold. the landlord has been told about this issue on more than 2 occassions. she told me to go buy the materials and fix it. she also stated that I cannot deduct the cost of materials from rent. when we moved in we were never asked to sign a lease, What can I do. I have 2 children in the home, and there is 3 rooms of my home that I had to close off. I am extremely allergic to mold and have been constantly sick this year.