Pressure in the back head+blackout+sweat, face felt very cold. Heard white noise in the background. Was tired&hungry. Should I be concerned?

Yes. Do not ignore particularly u black out? See your doctor.
?? of "blackout" It sounds most like low blood sugar, but whatever it is, if you have had it more than once, i would be concerned. See your health care provider to take a more extensive health history, do a physical examination and get whatever additional tests are needed.