Is that normal to feel out of it, tired and a bit dizzy after an orgasm?

Post coital symptoms: During coitus and orgasm, there is shunting of blood away from many of the organ systems and towards the genitalia. Orgasm is when this shunting is at a maximum. So, post-orgasm, it would not be unusual to feel a bit disoriented and fatigued. Being well hydrated (not with alcohol) may help alleviate some symptoms. Otherwise, i would recommend you relax post-coitally and enjoy the moment.