Hi Tye, understandable you feel like you cant trust your body but fortunately you have processed your own solution to how to cope!
If you look for an opening in conversation say discuss a dream you had last night or any such opening will appear, and then tell her " ive had this weird problem for awhile now, it doesnt happen often at all"(per your statement, 5 times a year this is TRUE)" but i dream im peeing and i wake myself up wetting the bed." Well,YOU said it so much better but you get the drift.
You will want provide a bed mat to put on the sheet (after intimacy and before you fall asleep) perhaps that can be discreetly bundled up and set it a closed kitchen trash bag maybe? There are washable ones and disposable ones with a sticky backing that wont scrunch into a ball.
On the plus side of the problem is, you are a mature adult and hopefully she is too and mature adults realize our bodies arent perfect. If she is a woman in your decade she probably has some body issues or insecurities she is concerned about too. Its a rare woman that doesn't.
So being upfront before hand might be one key to creating a lasting relationship.
Many men here will tell you they have much more incontinence than you and they met or are with a Life partner who finds it a minor issue or nonissue because they love the man warts and all.
Glad you found your voice and came here!