First it will be helpful to have your car year/engine. Check the usual mechanic stuff as others said. Brake pads thickness, fluid level, wires damage, fluid leaking fromthe master cylinder/HCU, excessive wheel bearings . If everything seems alright, go somewhere to have your code reads. Tell me when you will have your codes, i have the how to to diagnostic ABS.
And stop unplugging your battery, if the light goes on that mean something, don't try fooling your car, and you, that everything goes normal.
Nic.
