Hi Cally,
He may have told you that he likes you but he doesn’t want to ruin the friendship because he may not have a particularly good track record when it comes to romantic relationships.
In other words, he may have a history of short-lived romantic relationships that may not have ended well.
Hence, he knows that if he were to pursue a romantic relationship with you, not only will it be short-lived but it may end badly as well.
If it ends badly with you, not only would he have lost a short-lived girlfriend but he would also lose a friendship.
Hence, he may believe that it would be best not to pursue you as someone with romantic potential due to his past experiences.