What Trinity?

Matthew 3:15 16 17 "And Jesus answering said, suffer it to be so now for thus it becometh US to fulfill all righteousness.  Then he suffered him and Jesus, when baptized, went up straightway out of the water: and lo, the heavens were opened unto him and he saw the spirit of God descending like a dove, and lighting upon him and lo a voice from Heaven, saying, this is my beloved son, in whom I am well pleased" US? I know what 1st John says about them all being one, but what I don't understand, is why does God consistently talk to himself, and why if they were one, would he say, It becometh US? I find it more then a little odd that he told everyone that he was pleased with HIMSELF. Obviously an egomaniac and a great ventriloquist. : )