The only sin that is unforgivable is if you deliberately challenged (blasphemed) the Holy Spirit (Matthew 12:31-32; Mark 3:29) who is supposed to convict you of your sin.

The Holy Spirit will convict the world concerning sin and righteousness and judgment -- John 16:8 (ESV)

If the Holy Spirit can no longer convict you of your sin, who or what else will?

If you worry about unforgivable sin, then most likely you are not there. Not yet. Hearts with settled hardness against Jesus and his Spirit don’t go around worrying about it. -- David Mathis (desiringGod)

Moses made it clear that when someone knows the truth and still stubbornly rebel against it, God would not forgive him:

Beware lest there be among you a man or woman or clan or tribe whose heart is turning away today from the LORD our God to go and serve the gods of those nations. Beware lest there be among you a root bearing poisonous and bitter fruit, one who, when he hears the words of this sworn covenant, blesses himself in his heart, saying, ‘I shall be safe, though I walk in the stubbornness of my heart.’ This will lead to the sweeping away of moist and dry alike.

The LORD will not be willing to forgive him, but rather the anger of the LORD and his jealousy will smoke against that man, and the curses written in this book will settle upon him, and the LORD will blot out his name from under heaven. And the LORD will single him out from all the tribes of Israel for calamity, in accordance with all the curses of the covenant written in this Book of the Law.

-- Deuteronomy 29:18-21 (ESV)

Note that "stubborn" does not mean to be deceived, or to accidentally sinned or make a few mistakes. It means to deliberately and rebelliously choose not to obey God.

If you feel convicted, then it means that the Holy Spirit is still working on you and have not abandoned you yet.

But you might say: "I am a very bad person!"

If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. -- 1 John 1:9 (ESV)

• Have you blasphemed the Lord? -- The Lord will still have grace! (Mark 3:28)
• Did you swear a vow before God (marriage vows, courtroom vows, secret organization vows, etc.) that you regret? -- If the High Priests could set those people free (Leviticus 5:4-10), why would Jesus Christ not qualify?
• Did you deny the Lord in public? -- The Lord will still have grace! (John 21:15)
• Did you abort your own baby or murdered a person? -- The Lord will still forgive you! (2 Samuel 12:9,13; Psalm 51)
• Are you a prostitute? -- The Lord can set you free! (Matthew 21:31; John 8:6-11)
• Are you currently a criminal? -- The Lord will still forgive you! (Luke 23:39-43)
• Are you practising witchcraft or the occult? -- The Lord is stronger! (Acts 8:6-24)
• Did you persecute God's children? -- The Lord will still have grace! (Acts 8-9)

All of the above is wrong, but no matter who you are and what you had done, there is hope.

The Lord can set you free from your sins and your circumstances!