Can Someone Tell Me What This Fear Is?

This sounds a lot like Obsessive Compulsive Disorder. I'm no doctor, but just speaking from experience, these are classical symptoms. I would advise going to your gp and getting a referral to a mental health specialist. They will be able to help you, things will pick up again. It sounds like these thoughts are seriously distressing; all the more reason to get help as soon as possible. Don't turn to medication if you can help it, CBT (Cognitive Behavioural Therapy) is brilliant at dealing with the anxiety and panic attack side of things. I hope all goes well for you.