Hi, i aim to be a pilot in the RAF or RN when i have done my A-levels and Degree but recently went on holiday to florida and went on some of the worlds best rollercoasters! Thats the good bit

The worrying bit is that sometimes whilst riding the rollercoasters all of the blood would rush to my head and although i was fully conscious sometimes my sight would begin to blackout.
This also happened to a few of the other people i was with, does this mean that i would not be able to be a pilot? Or was it just from being really relaxed after queuing for ages from being exposed to a fair amount of G-force?
Any help would be appreciated?
Thanks