Can I divorce my spouse because of his fornication with other women before our marriage. †I was not guilty of the same. †It bothers me after all these years and I find it hard to forgive. †He says it was not a sin against me, but I feel the pain. †And even though we have been married almost 30 years it bothers me.
"And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery" (Matthew 19:9).
In the Greek Jesus' statement is about divorcing a spouse because of an on going problem of fornication. He is not talking about a one time event or something that occurred in the distant past.
I assume you knew about his sins before you married him, if so you entered a covenant with this man knowing who he was. Even if you found out afterwards, you remained with him for years. It is clear that these were past sins. He has been faithful in his marriage to you. He has not broken his covenant with you. This indicates a man who has repented of his sins.
He is correct that his sins were against himself. You were not in the picture at the time. "Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body" (I Corinthians 6:18). You are demanding the right to forgive a man of a sin that was not committed against you. It is a right that you do not have.
The man in I Corinthians 5 was withdrawn from for his fornication. Later he repented and in Paul's second letter, he says, "This punishment which was inflicted by the majority is sufficient for such a man, so that, on the contrary, you ought rather to forgive and comfort him, lest perhaps such a one be swallowed up with too much sorrow" (II Corinthians 2:6-7). The withdrawal accomplished its end in bring about a change in the man. Now that he changed, the required action by the church was to forgive.
But the shameful thing is that your husband has changed and left his sins behind. Yet, his wife, who claims to be a Christian, is holding it against him. Even if you wish to claim that these sins were against you, you should have forgiven him because he changed. "For if you forgive men their trespasses, your heavenly Father will also forgive you. But if you do not forgive men their trespasses, neither will your Father forgive your trespasses" (Matthew 6:14-15). If you can't forgive a repentant sinner after all these years, why do you expect God to treat you differently because of your sins?
My guess is that this really isn't about his past fornication. You simply want out of your marriage and in your mind this is a more justifiable cause for not liking your husband than the actual reasons.