You changed your response. Earlier, when I brought it up, you said Thomas was talking to both Jesus AND God. Now, you say it was just an exclamation.
Point of interest: the New Testament of the New World Translation was based on the Westcott-Hort Greek New Testament. (Not that any of the "translators" had any real knowledge of Greek.)
Remember how many times we've been told by the KJV cult that Westcott and Hort denied the deity of Christ? This is where Westcott gets his revenge:
The words ["My Lord and my God"] are beyond question addressed to Christ (saith unto him), and cannot but be understood as a confession of belief as to His Person . . . expressed in the form of an impassioned address. The discipline of self-questioning, followed by the revelation of tender compassion and divine knowledge, enabled St. Thomas to rise to the loftiest view of the Lord given in the Gospels. His sublime, instantaneous confession, won from doubt, closes historically the progress of faith which St. John traces. At first (ch. i. I.) the Evangelist declared his own faith: at the end he shews that this faith was gained in the actual intercourse of the disciples with Christ. The record of this confession therefore forms the appropriate close to his narrative; and the words which follow shew that the Lord accepted the declaration of His Divinity as the true expression of faith. He never speaks of Himself directly as God (comp. v. 18), but the aim of His revelation was to lead men to see God in Him.
B. F. Westcott, The Gospel According to St. John (London: John Murray, 1892), p. 297, underlining added.
Wesgcott's argument is that John confesses his own faith in 1:1 ("the Word was God"), and that the entire Gospel was leading up to Thomas's confession, in order to show how John, too, came to the same confession.
Note also that Westcott says "the Lord accepted the declaration." If Thomas was merely uttering an oath out of surprise, as we do, a form of "OMG," we might reasonably expect Jesus to rebuke him for blasphemy or swearing. But Jesus takes Thomas's exclamation at face value, and pronounces him blessed.