What do you mean by "official"? If you weren't together yet, then it's not so terrible in my opinion.. also, what makes you think he's changed? If he hasn't been cheating on you for more than a year, then he might be tellign the truth.

Often, people don't cheat becuase they don't love - sometimes they're just not sexually satisfied, or maybe others just want to break the "rules", I think it varies. I think you should talk with this to him if you haven't already