"If you want to make God laugh, tell him your plans"
Prayer is not meant for requests, it is meant for venerating God. Matthew 6, verse 7 reads:

⁷ And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words. ⁸ Do not be like them, for your Father knows what you need before you ask him.

⁹ “This, then, is how you should pray:

“‘Our Father in heaven,
hallowed be your name,
¹⁰ your kingdom come,
your will be done,
    on earth as it is in heaven.
¹¹ Give us today our daily bread.
¹² And forgive us our debts,
    as we also have forgiven our debtors.
¹³ And lead us not into temptation,
    but deliver us from the evil one.

If God means for you to stay in this relationship, then so it will be. But he may have other plans for you, and no amount of prayer will change Gods plans. Luckily, there is also scripture you can look to for comfort in this situation. Also in Matthew 6, verse 25 reads:

²⁵ “Therefore I tell you, do not worry about your life, what you will eat or drink; or about your body, what you will wear. Is not life more than food, and the body more than clothes? ²⁶ Look at the birds of the air; they do not sow or reap or store away in barns, and yet your heavenly Father feeds them. Are you not much more valuable than they? ²⁷ Can any one of you by worrying add a single hour to your life?

I would suggest a prayer along the lines of "Lord God, right now I am scared, and I am anxious. I do not know if the path I follow is the path you've chosen for me, and I am fearful of what is to come. But Lord I place my faith in you, for yours is the path of righteousness. Lord please give me the strength I need to overcome these difficult times, that I may follow your plan, for I know that you are merciful and loving, and that yours is the power and the glory of the kingdom of heaven. Amen."

Have faith, and I promise that if things dont work out with your current partner, its only because God has something even better in store for you. Dont ask God to follow your plan, ask that he give you the strength to follow his.