Before you think of taking him back, try to remember what you had gone through when you were with him. Was it a happy relationship? Did he cheat on you before? Because if he did, then he is probably doing the same thing now to his current girlfriend, so beware. Second chances in the relationship are glorious if two people who were separated are still in love. However, do not be the reason why he will dump his girlfriend. I think it is not a sign of maturity when you jump from one girl to another right away. If you are a matured person, you will break away from the relationship properly and give yourself some time to be ready before committing again to a new relationship.