I take long , hot baths and showers and when i get out i feel weak and light headed and feel like im about to pass out ... why?

Vasodilation.: Hot water causes your temperature to rise and your peripheral blood vessels to dilate. This may increase the volume of your circulatory system rather dramatically. If your blood volume is a bit on the low side ( as may happen in the am ) you can drop your blood pressure enough to get light headed. Sometimes people can pass out in a hot shower.