Why would you say that Jesus is the Jehovah of the Old Testament if that is your belief?
God revealed himself to the Israelites throughout the Old Testament. Most people would consider Yahweh to be God the Father in the Christian viewpoint. While this is not a wrong way to approach the Old Testament, there are places in the Bible where Yahweh (Jehovah) is revealed to be Jesus, the Messiah.
First, consider that the Old Testament looks forward to the coming of the Messiah. Everything from the temple structure to the laws of Israel to the sacrificial system looks forward to the perfect, sinless sacrifice that restores the relationship between God and humanity.
Jesus is the Messiah who fulfilled all of the prophecies and foreshadowing of his coming and his Person. So everything in the Old Testament looks forward to him and foreshadows his arrival. The Messiah prophesied in the Psalms and the Prophets as well as parts of the Torah and even in that Historical Books is perfectly fulfilled in Jesus.
That is a study much too large for one answer to your question. But this is the first place I go to explain that Jesus is all throughout the Old Testament Scriptures. The New Testament writers sometimes go to great lengths to show how Jesus has fulfilled the Scriptures.
Second, Jesus declares himself to be the fulfillment of the Old Testament Scriptures. After Jesus is resurrected from the dead he appears to the disciples and tells them that he is the fulfillment of Scripture (Luke 24:27, 32, 44-48). Jesus says that he came to fulfill the law (Matthew 5:17-20).
Third, in John 12:41, John attributes passages Isaiah spoke about the blindness of the religious leaders to see Jesus for who he was, the divine Son of God. In that verse he says that Isaiah said these things because he saw his (Jesus’) glory and spoke of him (Jesus).
When did Isaiah see Jesus’ glory? If you look at his commissioning and Isaiah 6 Isaiah speaks of “seeing the Lord (YHWH)” seated on his throne and his train filled the Temple. Isaiah further describes the glory of the Lord. John makes a clear link between seeing the glory of the Lord and Jesus’ glory.
Beyond this, being called the Christ or Lord throughout the New Testament would have been the words he used of the Messiah and Yahweh respectively. The word for Lord would be the equivalent in Greek of the Hebrew Yahweh. Christ is the equivalent of the Hebrew word Messiah.
In a few places throughout the Gospels Jesus declares himself to be divine and one with the Father. John records many of his references to his equality with the Father (John 5:19; 10:30; 14:9; 17:21). But he is not the only Gospel writer to record Jesus speaking this way. Matthew also mentions it ().
John uses seven “I Am” statements throughout the first half of his Gospel in which Jesus declares himself to be equivalent with God. The Greek Ego eimi (I AM) are the same words used for all of the references to Yahweh in the Septuagint (Greek translation of the Old Testament).
The tetragrammaton (four letters YHWH) is translated into Greek this way, and this is how Jesus uses the formulation of the “I AM” statements. He declares himself to be not only God, but Yahweh.
The Pharisees and religious leaders of his day understood his claims to be Yahweh and divine. This is why they say he is a blasphemer and has a demon, and are zealous to kill him. He states in many ways his divinity and equality with the Father.
Fourth, Jesus is the Angel of the Lord seen throughout the Old Testament Scriptures. I would say that every single angel of the Lord parents is not the pre-incarnate Christ. But many, if not most, appearances of this Angel of the Lord do seem to be a divine being.
The rule of thumb is that anytime you see the Angel of the Lord accepting worship or sacrifices from people he must be a divine being. Angels do not receive worship from people. Several times in the book of Revelation John the Angel is guiding him and the angel tells him to get up. But throughout the Old Testament when the angel of the Lord appears he sometimes accepts worship from humans.
Some of the prime examples are when the trinity makes a rare appearance to Abraham (Genesis 18:1-8) and tells him Sarah will bear her son Isaac within the year (Genesis 18:10). Then he discusses with Abraham how he is going to destroy Sodom and Gomorrah and how he will not destroy the city for ten righteous people (Genesis 18:22-33).
Another example is when the angel of the Lord wrestles with Jacob. The text says that he literally has “striven with God” even though he is facing an angelic being (Genesis 32:27-30). Gideon needs with the angel of the Lord and the Angel takes his offering and turns it into a sacrifice, burning it with fire (Judges 6:19-21). Gideon is afraid he’s going to die because he is seen angel of the Lord (Judges-24).
The Lord elsewhere has said that if anyone looks upon his face he will die (Exodus 33:20). There are two possibilities here. The angel of the Lord represents the Lord himself and therefore has his authority.
But it is more plausible in many of these circumstances that you’d love the Lord is the pre-incarnate Christ, divine and able to receive worship and sacrifices from humanity. If this is the case, then the angel of the Lord is a theophany, and occurrence of God appearing to humans himself. And if that is the case the pre-incarnate Christ is the one they are seeing.
One example of the angel of the Lord not being Jesus is in Luke 2:9 when the group of angels in the sky declare what is happening in the coming of Jesus. But all of these examples show how Jesus is Yahweh through New Testament revelation.