Relationships with a babg

My boyfriend and have been bestfriend for 5 years and been together for 2, we have a great baby boy, however we never really fought before our son, and now everyday we seem to get into little arguments about something, we are both pretty tired most of the time. Our relationship is still strong and I have never thought about leaving him, he is the love of my life and a wonderful father to our son. I just would like some advice of how not to fight everyday, it's nothing really big, just things about how I would like help and that I need my time still too, and he thinks even though hes gone from the house it's not a break to him (he goes to the gym every other day, and works through out the week) I try to talk to him about helping me more and I won't be so grumpy when he gets home from work. But everytime I try to talk to him about he gets defensive and we start to fight about it.