I've found this one very helpful for a similar although not identical situation:
1 John 5:18b He who was born of God keeps him, and the evil one does not touch him
Have you had much exposure to praying the scriptures? You can personalize them & there are at least 3 different ways you can say them.
1. Thanksgiving
Thank you Jesus that He who was born of God keeps me, and the evil one does not touch me
2. Warfare - standing against the enemy
It is written: He who was born of God keeps him, and the evil one does not touch him
3. Declaration of faith (Let the redeemed of the Lord say so)
I believe He who was born of God keeps me, and the evil one does not touch me
What I recommend is saying each one repeatedly before moving on to the other so you get into the spirit of each. Make this adjustment as you move from one to the other.
#1 can have a spirit of peace & protection about it
#2 has an attitude - really engage the Spirit in you as you say it. You are indwelt by the Holy Spirit of God - like the ark of the covenant. How dare the enemy even attempt something like this. When people did irreverant things around God's presence in the OT, fire came out & consumed them (eg Lev 10:2, Num 16:35). How much more should this be the case for a purely evil being.
#3 has a confidence about it. Speak it from a sense of "this is God's truth about the situation"
Playing praise & worship music in your room at night would also help. If you sing, you could sign a long with it & get a sense of God's presence & then lie down & sleep in that "place".