If you think that saying one word on accident will make God up and abandon you, I think you need to adopt a higher view of God. He isn't waiting around looking for an excuse to leave you.
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For I am confident of this very thing, that He who began a good work in you will perfect it until the day of Christ Jesus." (Phillipians 1:6)
"This is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day." (John 6:39)
"If we are faithless, He remains faithful, for He cannot deny Himself." (2 Timothy 2:16)
If you are saved, God will not leave you. He will remain faithful to save you and keep you, despite the stupid mistakes you make.
Also, try to stop praying these "please don't leave me" type of prayers. You're begging for something you already have. As someone who's gone through the exact same fears as you, I can say this type of fear is dysfunctional. It's like a kid begging his parents not to disown him. The only kids who would do something like that either have no concept of reality, or they have been emotionally abused. You've been abused by OCD, which tells you that God is too weak to save you and your salvation depends on your own efforts. THAT'S WRONG! DON'T LISTEN TO IT!
Instead of praying that God will not leave you, pray that he will remind you that he will be with you until the end of the age. Instead of praying that he take your thoughts away, pray for strength to serve him in spite of the thoughts, and the strength to complete your treatments (btw, are you seeking any sort of behavioral therapy for your OCD? Drugs alone don't help most people long term).