You can deny the truth, but it won't change what that "my God" is used in reference to Jesus in Jhn 20:28.
1. BDAG (3rd Edition): Concerning John 20:28 states that theos "certainly refers to Christ" (theos, page 450).
2. A Greek and English Lexicon of the New Testament: Of the Logos, who is declared to be ho theos, e.g. John 1:1...also in the exclamation of Thomas, John 20:28. - So Christ is called ho theos (theos, page 334)
3. New International Dictionary of New Testament Theology (NIDNTT): Jn. 20:28 contains the unique affirmation of Thomas addressing the Risen Christ as God: "My Lord and my God [ho kyrios mou kai ho theos mou]." (2:81, God, J. Schneider).
4. Theological Dictionary of the New Testament (TDNT): the Risen Lord discloses Himself to Thomas, and the astonished disciple exclaims: ho kurios mou kai ho theos mou (Jn. 20:28). In Jn. 1:1 we have Christology: He is God in Himself. Here we have the revelation of Christ: He is God for believers. (3:105-106, theos, Stauffer)