Talk it out, try to figure out why you guys have suddenly started to fight.
Or, when you two get into a fight you could write a letter explaning why you got made at them and then write at the end about how you didn't mean to get angry at them and then give them to each other.
You may need sometime to yourself also, perhaps spending all your time together has made you guys start to get annoyed at each other, maybe you guys can spend slightly less time with each other.