Then the high priest rent his clothes, saying, He hath spoken blasphemy; what further need have we of witnesses? behold, now ye have heard his blasphemy. What think ye? They answered and said, He is guilty of death.

Yes, you are right. He not only said 'Y'ho-vah' when he was speaking but many times he said y'yay asher y'yay

I am who am

That would have definitely been blasphemy, if he were not God in the flesh.