dear Sister, please do not be offended. i am struggling with a similar circumstance, well kind of.
i was married to my christian husband for almost 20 years. he had been saved, but wandered from God and was severely emotionally abusive to me and our children. i prayed for years, my whole church prayed for years, and finally i left my husband. because of methamphetamine he was a changed man, no longer the loving man i married. i finally felt God was leading me to leave him, or i never would have. my minister and church family had encouraged me for years to leave him.
eventually my husband found a girlfriend and divorced me. now for the last 7 years i have lived with a man without the benefit of marriage; a man who is not a christian.
about two years ago my ex-husband moved in with us! his girlfriend never really cared for him and when he figured that out, he left her and has been living with me and our kids (and my boyfriend!) ever since.
anyway, it's really a weird situation, but about a week ago my boyfriend told me he is leaving (hooray!) i was trying to figure out how to tell him i wanted him to leave without hurting him. i believe he overheard me telling my son that i did not love Steven (the boyfriend) and he became extremely angry and told me he was leaving. once again, HOORAY! he is an ungrateful, nonChristian, lazy man who treated my kids terribly and i can't wait for him to leave!! he lost his job last october and has remained unemployed, has not even looked for a job. i support all of us

. my husband is the same way, unemployed and i support him also, and our kids.
once Steven leaves, this leaves me and my husband and our kids in the home. i love my husband Michael and i never stopped. i only left him at God's leading, because of his drug abuse and emotional abuse toward our family. but i never stopped loving Michael, nor he me.
the problem is, Mike just got out of jail after being in there for 6 months for methamphetamine use, so he is still using. as a matter of fact, the day he got out of jail, i saw signs that he had snorted some meth (or however he does it) and he was high when he came home from jail. i can always tell. that stuff makes him so weird and not himself. it takes his mind away. it's like he can't focus or think when he is on it. just babbles ridiculous and even evil stuff. really weird and sick.
so i don't know what to do. i am glad Steven is leaving, i just pray he leaves peacefully. but i am in a quandary as to what to do with Michael. i love him and he loves me, but he is still using drugs.
also, another consideration is, he has been with maybe 50 women since i left him (not kidding, he's kinda cute and very cuddly..lol). and i am concerned that he may have been exposed to STDs or AIDS. i have heard that HIV takes sometimes 10 years after infection before it shows up on a test, so i don't want to have sex with Michael, and what kind of a marriage is that?! i'm sure that would be unacceptable for Mike.
okay, that's my story. but when i read your post, the first thing i thought was that you are still married to your first husband, according to the Bible. i have always felt that i am still married to Mike. some paper that a judge signed does not make a divorce, not in God's eyes. Michael was and always will be my husband. at least that is how i interpret scripture. but i have been wrong before, so am not sure.
anyway, if you are still married to your first husband, then the second hubby you are having adultery with, so you should return to your husband? i'm not sure. so confused. sorry to throw this at you. i just think marriage is forever and that is how i interpret Scripture to say also. but like i said, i know there are others who interpret it differently. i can't see how though, since Jesus said, Luke 16, verse 18. 18"Anyone who divorces his wife and marries another woman commits adultery, and the man who marries a divorced woman commits adultery.
also in Mark 10, verses 1-12, it says
Divorce
1Jesus then left that place and went into the region of Judea and across the Jordan. Again crowds of people came to him, and as was his custom, he taught them.
2Some Pharisees came and tested him by asking, "Is it lawful for a man to divorce his wife?"
3"What did Moses command you?" he replied.
4They said, "Moses permitted a man to write a certificate of divorce and send her away."
5"It was because your hearts were hard that Moses wrote you this law," Jesus replied. 6"But at the beginning of creation God 'made them male and female.'[
a] 7'For this reason a man will leave his father and mother and be united to his wife,[
b] 8and the two will become one flesh.'[
c] So they are no longer two, but one. 9Therefore what God has joined together, let man not separate." 10When they were in the house again, the disciples asked Jesus about this. 11He answered, "Anyone who divorces his wife and marries another woman commits adultery against her. 12And if she divorces her husband and marries another man, she commits adultery."
so, in God's eyes, isn't marriage forever? i'm so confused. maybe God wants you with your ex-husband? maybe because he is atheist, God does not. i am uncertain. do you have a pastor who you trust who could counsel you?
i did not mean to take over your thread. i will add you to my prayer list and pray for you for the next week, Sister in the Lord. God bless you and your family.
dear Father, i love and praise You. dear Lord, we ask forgiveness for our sins and that you would show us the way out of the mess we make of our lives. i desire only to live for You, Lord. i pray you will guide this sister's heart and let her know it is from You, Lord. show her what to do. i am saddened, Father God, that there is so much pain from the mistakes we make when we don't follow you. i am sorry, Lord. please forgive and bless me, and my Sister also. bring her discernment through the blessed Holy Ghost. thank you, Jesus. i ask all these things in Your holy name. amen.
please pray for me too, Sister.