Hi, im new here but i was wondering if anyone knows any medical reasons for my 'problem'.

I am 16 and since i became 15 i will some times have a very short period where i will black out but only in motion (When moving). Usually before this happens i will feel a sense of dizziness, loss of sight in both eyes, loss of balance and muscle fatigue (Weakness) but i will never fall to the ground or collapse but will feel a sense of my body dropping and then a sudden shock to my system which then all the problems disappear apart from feeling confused with my sight being reduced for a short period of time after this happens. I was wondering if anyone else has this feeling or what the reason is for the 'problem'. Thank you.