My instinct on the text is to reply lightly saying 'thanks for letting me know. I appreciate it' (or similar) and leave it at that. I think it'd be a good idea to reward his 'good' behaviour, i.e. regret and thinking of you, as well as contacting you, but not in an overly effusive way.
Him being sorry is good- a sorry and an expression of regret was the first baby step I got from H. On the other hand, I wouldn't recommend getting upset again. He knows he's hurt you. Now show him what he's missing out on!
