The waiting is the hard part but it will be nice when you finally know the type of myotonia. It takes about six months to get in to a neurologist here and then they often refer you to a geneticist for the testing (another wait) and then you have to wait for the test results which can be several weeks.
Many of us weren't diagnosed until we were adults...it's not uncommon for doctors to dismiss the symptoms. I agree with Jenna, it's very unlikely that you would have myotonic dystrophy if you haven't seen other symptoms by now.