I have tried to analyze your problems associated with the response of your brain and your heart situation during the moment of reaching orgasm.
Generally speaking, black-out is a transient loss of consciousness, a result of inadequate cerebral blood flow due to too-low or too-high blood pressures, as follow the diffraction (deflection) of the orgasmic power surge into the heart.
Once a woman break her orgasmic barrier to full orgasm, she will have involuntary crying and shaking with a very heavy breathing, at a period of 0.8 second. The involuntarily vocal or body responses to the orgasmic power surge are driven by the shock wave of the cerebral blood flow and partially attributed to the direct shock wave of the orgasmic power surge. The orgasmic power surge runs out of the Epicenter, a location at the deep end of the vagina, between the uterus and bladder, coupled into an energy channel called Conception Vessel in the Chinese acupuncture network in the central line of the front body under the clitoris(the energy gate), to the forehead. When the powerful orgasmic surge travels to the middle point between two nipples, at the acupuncture point CV-17, a part of the surge energy is partially coupled into the Heart Vessel of the acupuncture network, and the major energy flux is continously pushed up to the forehead along the Conception Vessel. The major orgasmic power surge traveling along the Conception Vessel will be radiated out as heat waves on the head. This will stimulate the brain produce pleasure waves.
The orgasmic energy coupled into the heart will drive the heart to pump (produce) hydraulic shock waves in the outflow blood. The shock waves will shake in the entire body. The shock waves also travel with the cerebral blood flow into the cerebral cortex in the brain, which is the executive suite of the nervous system for all the conscious behavior. The shock waves will temporarily disable the function of the cerebral cortex to produce involuntary crying and shaking. After the shock waves are over, she will become soft. Sometimes, she wants her man to load his low body weight on her pubis. There is no way for a woman to fake orgasm except her man is very dumb!
If there is blockage in CV-17 or CV-18 (above CV-17), the orgasmic energy will be fully deflected into the Heart Vessel. This will overload the heart to cause too-low or too-high blood pressures in her body, that will black her out. If a too-low blood pressure blacks her out, she may get cold or chilly shocks after reaching orgasm.
If there is no blockage in the energy channel - Conception Vessel, she will feel numb in the face or entire body for few minutes when she experiences Level-7's multiple orgasms. Her body will be very soft after having such orgasms. This level of multiple orgasms is usually happened around her ovulation when her sex drive reaches the peak point.
Because we have produced different levels of multiple orgasms in every intercourse since we were young, naturally we know when we will get what kinds of orgasms and when we may experience some problems associated with the orgasmic power surge, so we have done the research for causes and developed methods to troubleshoot and prevent the problems. While we have never worried about archieving orgasms, we have been very carefull to test the prevention of the problems associated with powerful, multiple orgasms, in particular, in the high-temperature period 2 or 3 days after ovulating. It seems that the nature of women's sex organ doesn't welcome intercourse during the high temperature period, likely doing "some interior remodling." Women after 35 likely enounter sexual and orgasmic problems during this period.
The solution for you is to massage CV-17 and CV-18 in your front chest to make sure that the major orgasmic power surge travel along the Conception Vessel to your forehead for pleasure. In the foreplay, your man should massage your chest, not just play your breasts or suck your nipples.
A powerful orgasm will cause miscarriage after 4-5 month pregnancy! It is an earthquake inside the uterus!

Special Note: If there is blockage in the area between the navel and the clitoris, powerful orgasm will produce cramps, pains and spasms in the low body, from the low abdomen, the grions, the thighs, and the perineum/ anus/ tail bone, to the legs/foots. This is because the orgasmic power surge is reflected into the Kidney and Liver Vessels to the low body, at the clitoris area under which the Conception, Kidney and Liver Vessels are interconnected together.