Okay, so you both sucked. Five years ago. Why exactly do you want to reach out and apologize now?
For the record, according to PBS and Muppets everywhere, it's never too late to fix a mistake.
However, what do you expect from this at all? Only reason I'm asking is because five years really is a long time to hold onto something when you admit that you both sucked as humans towards one another. You want to apologize and are you hoping that he'll do the same and that you two can rekindle the romance? Or is this just one of those "My Name Is Earl" getting right with life type epiphanies?
Point is, if you want to apologize then feel free. I'm just curious as to your motivation.