Aries man, capricorn woman. Bad combo?

I'm a capricorn (Jan 7) dating an aries guy (Apr 18). We've been together for a few months, everything's been great, except for a few fights we've had that have been quite intense and almost ended our relationship... And also I'm a little frustrated with the fact that he doesn't seem to want to define our relationship. Which makes me wonder, is this a bad combination?