I wouldn't rely strictly on your Greek to understand these verses. From: http://144000.110mb.com/trinity/index-7.html#35
Thomas called the resurrected Jesus “My Lord and my God” - (John 20:26 - 29)
The Jehovah's Witnesses also contend that even the apostles never thought that Jesus was God, but this ignores John 20:26-29 where Thomas, after witnessing the risen Christ, calls Jesus “My Lord and My God.”
The Jehovah's Witnesses reject this traditional Christian view and teach that Thomas thought of Jesus as no more than a special human occupying a “position far higher” than men and judges who were addressed as “gods” in the Old Testament (see John 10:34, 35 RS; Ps 82:1-6) (Reasoning, 213). Thus, Jesus was “like a god” (Should You Believe, Chapter 9). They also suggest “that Thomas may simply have made an emotional exclamation of astonishment spoken to Jesus but directed to God” (ibid.).
First, this position ignores the common sense fact that Jesus had just appeared out of thin air, risen from the dead, and any Old Testament comparison to special god-like men are woefully misplaced.
Secondly, Thomas was engaged in a direct conversation with Jesus, not God in heaven, when he uttered those words. He answered Jesus who replied to him in return and nothing in those verses remotely suggests Thomas was speaking to the heavenly Father or referring to Him.
Eight days later, his disciples were again in the house, and Thomas was with them. The doors were shut, but Jesus came and stood among them, and said, “Peace be with you.” Then he said to Thomas, “Put your finger here, and see my hands; and put out your hand, and place it in my side; do not be faithless, but believing.” Thomas answered him, “My Lord and my God.” (John 20:26-29 RSV)
Third, calling out “My God” in astonishment would have amounted to taking God’s name in vain and blasphemy in violation of Exodus 20:7 and Leviticus 24:16, crimes punishable by death.
Fourth, Thomas was fully cognizant of the many miracles Jesus performed, in addition to Christ’s implicit and explicit references to himself as God. It truly stretches credulity to think that Thomas thought of Jesus as nothing more or less than a resurrected man. Casting all doubt aside, Thomas knew that Jesus was his Lord and his God. His answer to Christ “forms a literary inclusion with the first verse of the gospel: “and the Word was God” (NAB notes John 20, 28).
Fifth, highly significant is Thomas’ use of “Lord” and the manner in which “Lord” is tied directly to God. Here, Lord refers to God in the supreme sense because there can only be “one Lord” according to Paul at 1 Corinthians 8:6, 7 and Ephesians 4:5. Although Lord (Greek kurios) has a wide application and can apply to men as a title of honor, such a lower meaning of Lord was eventually superceded by the higher meaning after Christ’s resurrection, and this is the meaning employed by Doubting Thomas.
(11) His purpose did not become clear to the disciples until after His resurrection, and the revelation of His Deity consequent thereon. Thomas, when he realized the significance of the presence of a mortal wound in the body of a living man, immediately joined with it the absolute title of Deity, saying, “my Lord and my God,” Jn 20:28. Thereafter, except in Acts 10:4 and Rev. 7:14, there is no record that kurios was ever again used by believers in addressing any save God and the Lord Jesus; cf Acts 2:47 with 4:29, 30.
(12) How soon and how completely the lower meaning had been superseded is seen in Peter’s declaration in his first sermon after the resurrection, “God hath made Him - Lord,” Acts 2:36, and in the house of Cornelius, “He is Lord of all,” Acts 10:36, cf. Deut 10:14; Mt 11:25; Acts 17:24. (Strong and Vine’s, 147)
“The full significance of this association of Jesus with God under the one appellation, “Lord,” is seen when it is remembered that these men belonged to the only monotheistic race in the world. To associate with the Creator one known to be a creature, however exalted, though possible to Pagan philosophers, was quite impossible to a Jew” (ibid., 147, 148 (16).
Sixth, as we learned earlier, (see section 23) ascribing to both Jesus and God a role which can only be filled by one “Person” must lead one to conclude that Jesus is God. So, if Jesus alone is Lord in the highest sense, and God is Lord, then Jesus must be God. If both God and Jesus are sovereign Lord and master over all and eternal savior, and there can be only one such Lord over all, then consequently Jesus must be God. Similarly, God is Lord of heaven and earth, but Jesus also has all power and authority in heaven and on earth. These roles are not mutually exclusive as there can only be one such sovereign when read together. Therefore, Jesus was, and is, God.
Given the above, the Christian confession “Jesus is Lord” at Romans 10:9 takes on a heightened significance in that Jesus is acknowledged not as mere man, or angel, but God. “[K]urios is the NT representative of Heb. Jehovah (‘LORD’ in Eng. Versions), see Mt 4:7; Jas 5:11” (Strong and Vines,147).
Seventh, Psalm 110:1 makes all of this abundantly clear. It says, “A statement of Jehovah to my Lord: Sit at my right hand, until I place your enemies as your footstool” (Green’s Literal Translation). The “Lord” of this verse refers specifically to Jesus, but this “Lord” in the Hebrew is adonay, which is “used as a proper name of God, only” (Strong and Vine’s, 6). “In the form adonay the word means “Lord par excellence or “Lord over all …” (ibid.). It is “used exclusively as a divine name” (ibid., 4). Jesus, therefore, was, and is, God, because Jehovah called Him adonay, Lord over all, and Peter also referred to Him as Lord of all (Acts 10:36).
Eighth, one of Christ’s disciples, Stephen, when stoned to death, cried out “Lord, Jesus, receive my spirit” (Acts 7:59). No doubt Stephen was familiar with Ecclesiastes 12:7 “…and the spirit returns to God who gave it” (RSV, Green’s Literal Translation). Stephen was not beseeching an angel to take back his spirit, but the Word who was, and is, God the Son, and who gave Stephen his spirit and to whom it would return.
Ninth, when Thomas said "My Lord and my God," he used the exact words that David used at Psalm 35:23 with reference to God, writing, "Awake, be vigilant in my defense, in my cause, My God and my Lord," (RSV, NAB, KJV and Green's Literal Translation). "Lord" here is translated from the Hebrew adonai used exclusively of God. Thomas would never have used these same words when addressing the risen Christ if he were just a man. The Jehovah's Witnesses' New World Translation changes verse 23 to read in part, "My God, even Jehovah."
