What Causes Recurring Facial Twitching And Numbness?

i m a 34 year african american female.i have numbness in my face at times my eye is twitching constantly. and sometimes my lip twitches and feels like there is twitching inside of my head. and my eye seem to be drooping. it started with my left eye now it is moving to the right. i fee like there is numbness around my four head and eye and sometimes seems like it is running down to my neck. and sometimes i feel off balance. i have has ealot of test over the last 2 years. mri's. cat scans, blood work. eye exams so fourth and so on. what could this be. and why are test that i'm having not showing up positive what should i do next. please help