Can I file for full custody with no lawyer

Can I do this and how? I am trying to get full custody because my bd is abusive and very inconsistent with our baby like he'll only see him 1 time per month and doesn't help with expenses. He is verbally abusive and puts me down all the time. Can I do this without a lawyer I don't have money for one and I'm so stressed right now because he threatens me to take me to court for custody