Did you create a new document to do this (as opposed to using an existing photograph)? If yes,, have a look at the image size (Ctrl Alt i). If you have created a huge document - many thousands of pixels on each side - then that would cause the default text size to appear tiny. Especially if you have used a low dpi setting like 72dpi. If this is so, then either start again with more sensible image size, or open the Image size dialogue box > turn off resample > and change the dpi setting to something _much_ higher like 300dpi.