One point that has not been discussed in this topic is the fact that the OP's wife gets a pain in her head when she has an orgasm. Now, I am not sure if this is somehting that happens every time or just once in a while so I will assume the worst case and go with all the time. Take a look at the following article about the sex headache.
FOXNews.com - FOXSexpert: Why Do I Get a Headache During Sex? - Sex | Erectile Dysfunction | Sexual Health
I suffer from them on time to time. They wipe me out completely. I feel absolutely exhausted after them.
As for having multiple orgasms, here is another questin. Is the OP speaking of clitoral orgasms alone? If his wife is like my Ex wife, she would have ONE HUGE Clitoral orgasm and that would be it! It took forever to acheive but would shake the earth when it did. (Not that I saw too many of them as she was a cold hearted beast who used sex as a tool to obtain her wants and desires. Do I sound bitter?)
Vaginal orgasms are another animal entirely. Those can be quite numerous and last for long periods of time. Hitting that elusive G-spot can bring about great pleasure for her and that may be your answer to the multi.
Hope this helps you!