Constant fear of death?

I use to be carefree but ever since I got my first panic attack I m afraid of everything. I constantly think about death and when I m going to die. Every time I get sick I worry I m going to die from it. I don t know how to just relax and not worry. My health is good as far as I know but I m still afraid I ll drop dead at any moment from anything. I don t even want to get out anymore