I'd make sure you tell whoever you live with that it happened.
If you happen to have a shower again and you do fall, you'll want someone to come help.
If you're worried about it (and having previously been anaemic is a fair reason to be worried) then you should go and visit your doctor. He'll probably give you a blood test, which will tell if you're Anaemic again or not.
If you're no longer supposed to be on iron supplements, then don't go taking them again without a doctor's orders.
But as everyone else has said, it's just possible that you had low blood sugar, could possibly be sick (and a bit woozy anyhow) or you could just have had the shower too hot and the temperature got to you.
If you have a shower seat, then try installing it. If you feel faint next time, try sitting down.
And for atleast a short while, it's probably best to leave your bathroom door unlocked, so that someone else in your house can come to your aid if you do fall again.
