Kathyrose - hi, it sounds like you have a temperature mixing valve for that shower head system that's out of adjustment. The expert plumbers here (which I'm not) can't tell you how to access it without knowing what type of fixture (e.g., Delta, American Standard) it is. But, you should be able to get to it either by removing some of the trim/cover stuff from the shower wall side or from the back side (through the adjoining wall - hopefully, there's an access panel already there). If nothing else, knowing the type of fixture you have would allow you to visit one of the big box home improvement stores where you can look at similar fixtures to see where you'd gain access to the valve. Also, their how-to books on plumbing may be of help. Good luck! Jim D/West Point, VA

You could have an anti scald type shower head that was popular several years ago to protect the elderly and children from scalding.

People felt it was a lot cheaper to install these types of shower devices then install a new shower body that has a pressure and or temperature balance built in