Is this some sort of mental illness?

I really need help, I can't relax at all, the though of surgery is ruling my mind, I broke off from cancer thinking 2 Years ago after horrible thinking, I used to sit alone in school after school outside only me and stare at the ground and think, but I broke it, now it's surgery and hospitals and cutting in surgery, it's scared especially My friend had surgery yesterday in her to nail and they took it off and cut and I watched a video and I'm so scared, I'm hopeless and.. I can't take it no more.. I can't do the stuff I enjoy no more without thinking , it makes me cry.. how does it feel standing for 10 minutes staring at no were and thinking until your head hurts.. I wanna enjoy my meals and time, not feeling like I have to go to jail after I eat or stuff
Please help me
please
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Is this some sort of mental illness?
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