Should I punch on today with one of my best friends?

So I've known the guy since primary school....We have always being good friends. We are the same age, but he is alot stronger than me and he always uses this to bully me....Whenever we have a verbal argument he will just punch me really hard in the stomach or kidney and I get angry but never retaliate physically. An example was at the supermarket when I jokingly bag him.....He always stays quiet at first but if I say something again he will lash out. He winded me in the supermarket and I shouted at him but he just dares me to hit him back, coz he will kill me if I try. I know our friendship sounds bad but we have a lot of good times together.....Anyway, I had an argument with him yesterday and he said he is going to hit me when we go to the gym today....What should I do....I really wanna hit him back but i know il get smashed if i do and i dont want to end our friendship coz we've hanged out for over 10 years.....He is just too serious and aggresive, but a good guy other than that.