After strenuous exercise (squats) i feel exhausted, lightheaded and dizzy, my vision goes white, my face turns very pale, and i need to lie down. why?

Deconditioned?: You may be exerting more than your body is able to support at this time. Is it only after squats? If so - positional changes may be affecting your blood pressure.

Hypotension : It's possible that your blood pressure is dropping when you squat . Please consult your doctor . He would check your blood pressure and listen to your heart to rule our murmur and might do an ECG to rule out other sinister causes.