Orthostatic hypotension is hypotension brought on by quickly moving up or down, such as getting out of a chair quickly. If you're standing and you take a step out of the shower, it wouldn't be orthostatic.

You did mention that you barely eat, so my hunch is your malnourishment combined with hot water and an environment with high humidity is the likely cause. Your blood pressure at rest is probably rather low, so additional vasodialation from the aforementioned environment would have led to vasovagal syncope.