I Was Lying In To Bath For About 30 Mins

I was lying in to bath for about 30 mins then Got up to have a shower and started feeling dizzy so I relaxed for a min and sat down then when I got up again the shower was still running hence it was pretty warm and started feel really dizzy and a horrible feeling of helplessness overtook my body, start seeing white slowly untill all I can see is white, what could this be
Eventually I made my way inside and sat down , then lay down and had a glass of water


Yes 2 factors I am fasting but have done nothing all day been in bed from 4am-1pm
Slept from 1pm to 5 pm and had plenty of liquid b4 I went to bed

It was very hot and when I moved fast all this happened , and now a few hours later any fast movement and I get light headed