as you have pointed out that saturdays always go a bit wrong - i can only assume the pair of you are drinking and then rowing and then last saturday he hit you. the solution is smple as you have identified the problem - stop drinking if you can't handle it yourself or deal with him when he's drunk.
you need to make a decision between going out on a saturday night, getting p!55ed with all your mates and fighting. you are behaving like a sheep - following others because you have no sense of personal direction, decision or standards. talk to him about it and see if he agrees and if he does, stay with him - sober on saturdays (the pair of you) - and have a more successful chance of a normal decent relationship, or carry on with your chavvy saturday nights out, continue being treated like sh!t, argue loads and potentially get into the routine of a battered pertner.
make your choice now and stick to it - and his behaviour will also affect what you do. if he chooses to continue drinking and behaving like an @rse, then you may have to decide on your own to leave him and live a more peaceful life.