You need to check yourself and find out why your self esteem is so low that you have fallen in love with an abusive person, who is an under age drinker. This boy of yours is a child, just like you.
Your kind of "love" is child hood love. You do not even have all of your teeth as of yet and are still growing molars, plus your brain is not even fully developed and you are not even finished growing...physically or mentally.
A boy, drunk or not, who puts his hand on a girl is not a boy worth calling your boyfriend.
But, you are young and like most children your age, you are invincible and always right, so nothing I tell you is going to make one bit of difference.
The mere fact that you came onto this web site to talk about being physically abused and not knowing what to do is a screaming clear indication that you are a confused and immature girl who does not recognize that drinking is wrong and so is staying with an abusive boyfriend.
One of these days, you will grow up and realize you are making a huge mistake in your choice of boys.