Many years ago I had a FWB with whom I was able to indulge my love of giving multiple orgasms. Our method was for me to be in charge of a dildo, while she was in charge of clitoral stimulation by means of her fingers.
Once she had orgasmed for the first time there would be a short period of rest, usually around a minute, until the vigorous dildo action would recommence with my friend applying just the right amount of stimulation that her sensitive clit could tolerate. She would orgasm again in a short time, usually with a lot of squirting. Another rest, and she was ready to go again. Twenty plus orgasms were no problem whatsoever.
My current partner is capable of multiple orgasms using a vibrator. I usually get to drive the bus until she has her first orgasm, then she holds our electric friend in order that she can apply exactly the kind of pressure that she can tolerate. Her second and subsequent orgasms take a lot longer than my old FWB, and a total of about four, or five, orgasms is as much as she can comfortably manage.
I wonder whether the OP could have more personal control in the process without taking anything away from her partner's pleasure kink?
As an aside, may I say how disappointed I am by the negative comments regarding the pain aspect? We are all different and this is a forum where we can learn about sex from others' experiences, so if there is something that you find beyond your own limits it is better that you make no negative comment and just sail on by.