Reem, are you able to get DNA testing? They almost never do muscle biopsies any more because they are usually inconclusive when you have MC. Did you have an EMG? That's the first step to diagnosing myotonia, but it won't tell you which type.
Is the stiffness just in your legs and feet? Those are usually the worst for us but it can also affect hands, face, abdominal muscles, etc. I hope you get some results soon. It's great to finally know what is wrong and that you're not crazy :-)