Christine,
I don't think you are being paranoid so much as you don't want to lose your husband and the life you have together.
When you combine the tragedies you've survived and your husband's past health problems, it's understandable why you would feel this way.
My own experience has been when life is going well for me is when I have times of fear it's going to be snatched away. In a way, it does take something away from me; my enjoyment of it.
Sometimes it takes some strong self-encouragement to let go and relax--hard for me to do even now. There are times it's easier to do than at other times, but I still give it a go.

Survivors sometimes have trouble believing that the good in our lives is going to last...

Peace and Power,
Cap