We understand your struggle with inner peace and your frustrations regarding your current relationship status. First, let's address the anger and bitterness you're experiencing. It's important to remember that God's ways are not our ways, and His thoughts are not our thoughts. For as the heavens are higher than the earth, so are His ways higher than our ways, and His thoughts than our thoughts. God desires for us to trust Him in all things, including our relationship status. Consider the words of Psalm 37:7-9 WEB:
Rest in Yahweh, and wait patiently for him.
Don’t fret because of him who prospers in his way,
because of the man who makes wicked plots happen.
Cease from anger, and forsake wrath.
Don’t fret, it leads only to evil-doing.
For evildoers shall be cut off,
but those who wait for Yahweh shall inherit the land.
It's clear that you harbor regret for not pursuing relationships earlier and feelings of inadequacy because you are still single. Remember, God's timing is perfect. It's never too late to trust God with your future. Also, it is better to wait on His timing rather than to rush into a relationship that is not His will for you. Remember, God is preparing someone for you, and this time can be used to prepare yourself to be a godly wife as per Proverbs 19:14.
Houses and riches are an inheritance from fathers,
but a prudent wife is from Yahweh.
Regarding your disagreement with Apostle Paul, let's consider his words in 1 Corinthians 7:7:
Yet I wish all men were like me. However each man has his own gift from God, one of this kind, and another of that kind.
Paul recognized that singleness is a gift from God for some, while marriage is a gift for others. Neither is a curse, but rather an opportunity to serve God in different capacities. It's important to align your thoughts with God's Word and see singleness as an opportunity rather than a curse.
Concerning your online interactions, it's clear that you've had some disappointing experiences. Remember, God calls us to treat others with kindness and respect, even if they do not reciprocate as per Romans 12:18.
If it is possible, as much as it is up to you, be at peace with all men.
It's also crucial to seek God's will in all things, including your interactions with others. Trust that He is working behind the scenes, even when situations don't go as you hope or even if someone does not respond to you as you would like.
Finally, you mentioned that you need a calm heart. Jesus says in Matthew 11:28-30:
Come to me, all you who labor and are heavily burdened, and I will give you rest. Take my yoke upon you, and learn from me, for I am gentle and lowly in heart; and you will find rest for your souls. For my yoke is easy, and my burden is light.
Let's pray together:
Dear Heavenly Father,
We come before You, lifting up our sister in Christ who is struggling with anger, regret, and disappointment regarding her relationship status. Lord, we ask that You grant her Your supernatural peace and patience that we can all only have by coming to Jesus Christ. Help her to trust in Your perfect timing and to see this season of singleness as an opportunity to grow closer to You and to prepare for the husband You have for her. Guide her interactions with others, both online and offline, and give her the wisdom and discernment to navigate these relationships in a way that honors You. Help her to realize that her worth and happiness should be in Jesus Christ and not depend on a relationship status. Lord, You know the desires of her heart, and You have a plan and a purpose for her life. Help her to rest in Your promises and to find contentment in You.
In Jesus' name, we pray. Amen.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
