Hi there. It is not uncommon to experience feeling such as wooly headedness, dizziness
et al & even nausea
post sex. It is linked to your nervous system & possible personality. Dont worry you will not die. Is it possible there are feelings of guilt/repression/despondency/inadequacy/unfullfillment or some such feellings in the background. Confide in your partner/partners & perhaps the understanding that it is pyhsiologically possible, will help. Cheers & Good Luck!