Jakki,
When I have sex with my G/F she often has an orgasm, sometimes not, sometimes multiple. She says it just happens that way. She has no discomfort nor after-pain.On rare occasions when we have mutual time to spare we treat ourselves to a "fest". All-on sex for two days/nights. I need the help of a pill or two but she has no problem responding. Sometimes she will have several orgasms quite quickly and repeat this over the hours. I do not often ejaculate but the sensation is the same. We are both in well trained physical condition but the stamina gives out in the end. It is not the multiple orgasms that beat her, she enjoys to the last.
My advice to you is:- Relax, let your mind be free of possible difficulties, go for it and see what happens. I don't think there is any physical nor mental difficulties that arise from multiple orgasms. You may discover a whole new avenue of your life to enjoy.