I'm in a new relationship with a man that's not well endowed. He is self conscious. How can I ease his mind?

Allow him to apologize as long as he needs to! Also, make the first move as much as possible, this lets him know that you want him. Send him messages and stuff arousing him and letting him know that he's desired. But don't discuss or try to persuade him that you like him the way he is, show him! It takes time...but when apologizes, just keep going...over time it will stop! Good luck and much respect to you.