We are made in God's image so it is best to look to His example for marriage - God wants marriage to be eternal covenant of love where there is washing of forgiveness - just like the covenant of Jesus with His Bride. However, one truly valid Biblical reason to consider divorce is adultery of another spouse and there are certain cases when being married to an unbeliever... but not all cases.
This is because God "divorced" spiritual adulterers (those who chased after other gods aka idols), so it is not sin to divorce an unrepentant spouse for adultery. BUT God forgives us when we repent, so if the cheating spouse honestly repents I'm strongly inclined to believe the Word commends forgiveness (Matthew 18:22), just as God has forgiven us. Even the Old testament example where God says in prophecy that He divorces His unfaithful wife, He later forgives her and restores her for His name's and glory's sake (Proverbs 19:11). If they dont repent and they want to continue their affairs, the betrayed spouse does not sin by divorcing them though. They have "departed" themselves.
Another case where divorce seems to be Biblical is certain cases, not every case of being "unequally yoked" with an unbelieving spouse. In this case the disciple of Jesus is married to someone who will not dwell with them in peace, but they abuse them, or cheat on them, or want divorce. The Word does not automatically command divorce if one is married to an unbeliever. In fact the Word recommends to stay in the relationship if possible, so the unbelieving spouse and the children would be positively influenced by the child of God. But if this unbeliever abuses the believer or wants divorce, it is lawful to part ways. It is the unbeliever that "departed" - the divorce did not happen by the desire of the believer.
1 Corinthians 7
10And unto the married I command, yet not I, but the Lord, Let not the wife depart from her husband:
11 But and if she depart, let her remain unmarried, or be reconciled to her husband: and let not the husband put away his wife.
12 But to the rest speak I, not the Lord: If any brother hath a wife that believeth not, and she be pleased to dwell with him, let him not put her away. (This is not said as a commandment, but as wise counsel. Seems to me that "being pleased to dwell with the believer" to also mean, not defying God and His ways in the house; if the unbeliever hinders the believer's faith or otherwise abuses them, how is that "being pleased to dwell with"? However, one should ask God personally for counsel and guidance on where to draw the line or whether it's fruitful to stay or not.)
13 And the woman which hath an husband that believeth not, and if he be pleased to dwell with her, let her not leave him. (again a conditional, if so, the believer should not divorce them)
14 For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband: else were your children unclean; but now are they holy.
15 But if the unbelieving depart, let him depart. A brother or a sister is not under bondage [to remain unmarried or be reconciled to them - Paul is referring to the earlier verse; there is no bondage because the divorce was not their desire or fault] in such cases: but God hath called us to peace.
I am praying that God will clearly show you what is His will and that His will is performed in your life. I'm also praying that your relationship with God gets stronger, and that you will turn to and receive His guidance, counsel and peace through this. Amen