How do i go about getting full custody of my son from mother?

Here recently ive found out alot of things about my sons mom. first of all she has warrents out for her arrest, she is staying in a tempory house with a friend that doesnt have any bedrooms for my son. she has admited both to me any my mother she dont have enough money for food. she has gottin kicked out of her moms house because she refuses to work and doesnt try to find a job. she cant hardly bye diapers and wipes for my 2 year old son. wich i do pay child support 75 a week goes to my son. not sure if this would be enough to get full custody. i feel like though she is not in the state right or mind to raise a kid. if someone would give me a answer i would apreciate it. thanks