Praise be to Allah.
You have to repent and seek forgiveness, and regret what you have done by getting in touch with men who are not your mahrams, and speaking to them and going out with them.
You must also cut off all ties with this second man immediately, with no hesitation, because the relationship between you is haraam.
How can you accept to be the cause of his divorcing his wife? If you were in her position, would you accept for your husband to divorce you in order to marry another woman who has come between you to spoil your lives?
We do not know how a wise man could agree to marry a woman when he knows that she has had a haraam relationship with a man before him and she has not repented from that relationship.
Whatever happened to chastity and protective jealousy? Does he not fear that this man may come back into her life again?
To put it bluntly, either this woman has repented or she has not. If she has repented from those relationships then there can never be any contact or relationship between them except in marriage. In this case there is nothing wrong with marrying her, but he should obey his mother, and not divorce his first wife.
If she has not repented from these actions, then it is not unlikely that she may form a relationship with a third man and a fourth.
Similarly, in your case, how can you agree to marry a man who is content to form haraam relationships, speaking and meeting with women? If he has repented, then there can never be any meetings between you, and if he has not repented, then a man like that cannot be trusted. His aim may be just to have fun with you, and even if he is sincere in wanting to marry you, there is nothing that would stop him from forming haraam relationships with other women.
Hence you have to cut off all ties without hesitating, and pray for forgiveness from Allaah for wasting your life in haraam pursuits. Turn to Allaah and ask Him to purify your heart and to remove all traces of those haraam relationships which have corrupted your heart and mind, let alone detracted from your religious commitment.
If you are sincere in repenting there is the hope that Allaah will bless you with someone better than him, and will make it easy for you to get married to a chaste and righteous man who will treat you in a decent manner and help you to attain the pleasure of your Lord, and you and he will form a believing family and produce good and righteous offspring.
Do not pay any attention to your heart and emotions, for in this case emotion has overpowered reason and religious commitment, and has harmed your spiritual and worldly interests. Your heart now is sick so you should not let it lead you to Hell.
Seek the help of Allaah, for He will not let down the one who seeks His help, and the one who humbles himself before his Lord will never lose out. Do a lot of righteous deeds, and seek righteous, believing female friends who can help you to deal with your worries and help you to obey your Lord.
And Allaah is the Source of strength.