The first thing I noticed here is that you were mothering him while you were together. It's not your place to help inspire he interests or make him grow as a person. You were trying to change him and that's not cool - and his initial reaction to what you were doing was not unexpected.
As for his about face, I'd be willing to bet that he's saying what he thinks it will take to get you back. Whether or not he can pull it off is another thing altogether. See if he can do it WITHOUT your help - because both of you need for you to stop mothering him
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.