How does siddhartha feel about himself

This depends on where in the book you are referring to. Siddhartha is a dynamic character: he changes.

Chapter 1

Although he brings joy to everyone's life, Siddhartha feels little joy himself. He is troubled by restless dreams and begins to wonder if he has learned all that his father and the other Brahmins can teach him. As Hesse says, "...they had already poured the sum total of their knowledge into his waiting vessel; and the vessel was not full, his intellect was not satisfied, his soul was not at peace, his heart was not still"