Can never find the right girl...?

Sounds like you are starting to mature and wants to start looking toward serious things in life.Since she knows you have been a player,let her know that you are more serious with her than the others.If she is serious about you then she will work on things for you and her to build something together that may last a lifetime.Trusting is something you both have to do together,and to keep the trust you have to be honest with each other.Good luck I hope you found or find what you are looking for.