Hi,
Welcome to HCM.
Fainting symptoms can arise when you have over-exerted yourself, when your blood sugar level is low, when you are too anxious, when your Hb% ( r.b.c ) in blood is low, inadequate
oxygen supply to your brain, low blood pressure or a combination of some of the factors illustrated.
To avoid such a feeling eat nutritious diet, include green veggies in your diet, keep yourself well hydrated,do not over-exert yourself, don't stand up too quickly,inhale plenty of fresh air, get blood tests done to detect you blood sugar level,
haemoglobin, etc, get clinically examined to check your fitness and get treated for low blood pressure.
See a doctor, if symptoms repeat. Don't worry you will get fine soon. Take are.