I have experienced the weirdest thing in the past few days...

I have taking my shower and washing my hair... I started not being able to breath so I opened the shower door so some air could come in. Then, I started getting really dizzy and starting to see double and I felt like I was about to faint.

I got out of the shower sat down for 2 minutes and went back in the shower. As soon as I got back in the dizzyness started again and then this huge tummy ache appeared. I had to get out of the shower again and go on the toilet bowl. I couldn't see nothing and my head was turning. I felt miserable for about 5 minutes. I had to get out of the bathroom but I couldn't even get up. I finally did and laid on my bed for 30 minutes until my dizzyness and tummy ache went away.

It couldn't be my menstruations cause I had 2 weeks ago.

I'm not sure what it is about the shower that could be triggering these episodes. Do you have general anxiety in your life? Have you had previous trauma in your life that the shower may be triggering? It's either a mental or physical thing, so I would get it checked out by the family doctor as soon as possible.
In the meantime, clean yourself by taking a bath and see if that also triggers it. Also, for the first few times you try the bath, have someone in the bathroom with you in case you start to feel faint again. If you get to the point where you can take a bath on a regular basis, try little stints in the shower (with someone present) to see if the episodes recur.
Also, it would be helpful to your doctor if you start keeping a diary of these episodes so he/she knows the circumstances surrounding them.
I hope that you see the doc soon and get an answer to this puzzling dilemma. Please, if you have time, let me know what the outcome is.
Good luck.
:-)
Kayti

Edit: Do you stand with knees locked in the shower? This can prevent the flow of blood from returning from the lower extremities and cause you to feel faint. I see it quite a bit in military formation.

It's possible you are dehydrated and/or getting overheated in the shower. Turn the water temp down, open the door to the bathroom (for more ventilation), and drink more water; see if it makes a difference.

I get the same thing and it is really bothering me.