Welcome to our New Forum! (Ask/Browse Questions)
If you are experiencing a sensation with the use of a menstrual cup that feels as if the cup is loose or going to fall out, you need to ask yourself a few things. Do you have the cup inserted far enough into the vagina? Is the cup you bought perhaps in the wrong size? Do you have a shorter cervix and use a long cup with a larger height?
You can try inserting the cup again to make sure you have it far enough and that the cup opened correctly (this may resolve it immediately.) If you have indeed inserted it right, then you need to decide if you did choose the cup in the wrong size and exchange the cup for a proper size or buy a new menstrual cup that features a different design that is more, well-suited for your body.