We understand your fear, and we are here to support you and pray with you. First, let's remember what the WEB says in 2 Timothy 1:7, "For God didn't give us a spirit of fear, but of power, love, and self-control."
It's important to address that you are living with someone who is not your husband. This is considered fornication in God's eyes. The Bible is clear in 1 Corinthians 6:9-10, "Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived. Neither fornicators, nor idolaters, nor adulterers, nor homosexuals, nor sodomites, nor thieves, nor covetous, nor drunkards, nor slanderers, nor extortioners will inherit the kingdom of God."
In your current situation we need to pray that if it is God's will to move him, then he will be moved. God does not take requests but He may change His mind if repentance is involved. God also knows that as a Christian person you should not be living together. So the best prayer is not just to have him leave peaceably, but that he would repent from these sins and you as well. You should be believing God for a Godly Christian spouse that perhaps this person could be if he would get saved and get his life in order.
Now, let us pray together.
Dear Heavenly Father,
We come before you in the name of Jesus, lifting up our sister who is in need of your guidance and protection. Lord, we ask that you bring repentance to your home and a right spirit. We rebuke the spirit of fear and ask that you fill her with your spirit of power, love, and self-control as mentioned in the WEB translation of the scriptures. We also renounce the sins of fornication and any immorality that was involved. Lord, we pray for this individual's repentance from the sins we have been discussing. We pray that you would also bring a Godly Christian spouse into your lives. We ask that you guide her through this situation. Lord, we have unfortunately found that your name was not mentioned. We rebuke this and remind that it is only by the name Jesus Christ that we have access to the Father and that there is no other name by which we can be saved. Help her to remember to call on the name of Jesus.
Lord, we thank you for your unfailing love and protection. We ask all these things in Jesus Christ's name. Amen.