We are truly sorry to hear about the struggles you're facing, and we're here to lift you up in prayer and offer some biblical encouragement. Firstly, it's important to remember that God is always with you, even in the darkest times. As it says in Deuteronomy 31:6 WEB, "Be strong and courageous. Don't be afraid or scared of them; for Yahweh your God himself is who goes with you. He will not fail you nor forsake you."
Regarding your depression and trauma, we pray that God's comfort and healing would envelop you. Remember the words of Psalm 34:18 WEB, "Yahweh is near to those who have a broken heart, and saves those who have a crushed spirit." God is close to you in your pain, and He cares about your suffering.
It's also commendable that you're praying for the girl you cared about. It's important to trust God with your relationships. God is in complete control of your life, and He uses the circumstances for your good and His glory even if they are hard and do not make sense. No matter how much it hurts right now, it is good to remember that God has the best in store for you. Regarding your past relationship with her, let's pray together. It is important that you did not become unequally yoked with a nonbeliever. For we are instructed not to be in a marriage with an unbeliever in 2 Corinthians 6:14 WEB, "Don't be unequally yoked with unbelievers, for what fellowship have righteousness and iniquity? Or what fellowship has light with darkness?".
However, it appears that you are still hurting from memories of her. We must look at this from a Biblical perspective. Many times we are allowing the past to control our emotions and thoughts. We are instructed in Philippians 4:8 WEB, "Finally, brothers, whatever things are true, whatever things are honorable, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report; if there is any virtue, and if there is any praise, think about these things.". We need to focus on godly things.
Also, you may be feeling this pain because you are possibly not completely forgiving her and possibly yourself for your past relationship. We are commanded to forgive in Ephesians 4:32 WEB, "Be kind to one another, tenderhearted, forgiving each other, just as God also in Christ forgave you.".
It is only by the name of Jesus that we have access to God. It is good that you mentioned Jesus' name in your request. His name has all the power in heaven and on earth. We pray this in the name of Jesus, knowing that it is by His name and His blood we receive salvation. "In him we have redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace," (Ephesians 1:7 WEB).
Let's pray together for all of this:
"Dear Heavenly Father,
We come before You, lifting up our brother in Christ who is struggling with depression, trauma, and heartache. We ask, Lord, that You would be his comfort and strength in this difficult time. We are so thankful that we can call upon your name because it is only by the name of Jesus that we can even come to you. Heal his broken heart, Lord, and help him to trust You with his past and future relationships. Give him discernment and wisdom and turn his pain into joy.
We also pray for his friends and those around him, that they would come to know You as their Lord and Savior. We pray for your provision for Christian friends and fellowship. Help him to forgive and heal from the past. Help him to focus on godly things and not his hurt. Use his story to draw others to You, Lord.
We ask this all in Jesus' mighty name, Amen."
Lastly, we encourage you to seek out Christian community, even if it's just one or two others who can encourage you and hold you accountable. Consider online communities if in-person ones aren't an option. We are a community that will pray for you. As it says in Hebrews 10:25 WEB, "not forsaking our own assembling together, as the custom of some is, but exhorting one another, and so much the more as you see the Day approaching."
Let's lift up these needs in prayer! 
