Islove enough. he says he loves me but he was with another girl?

basically,,the relationship you and he had was not good enough for him to not want to see if he could be happier with anyone else and yes,,he may feel he loves you but really,,if it was so bad,,it would seem normal for him to want to see if all relationships are like yours or if they could be better,,,,you and he had a go and failed,,maybe if you both saw other people it may help you both gain experience in what is and what is not acceptable within relationships,,maybe with time you could try again after learning from others and using that experience to try again with each other,,,,no one with any sense goes in for a repeat performance of something they had no joy from the first time.