Ok...I think the first step would be to be sure there is no medical condition that you do not know you have.
Next, would be to maybe try and talk to someone, like a therapist. They would know about sudden changes in behavior and possible phobias.
Whatever is going on, it is definitely something to take seriously. Even the doctor may have some ideas.
I have found in my experience, that it is not usually good to speculate. Doing something about it not only makes us feel better, but prevents our mind from thinking crazy things.