Hi Linda,
You might want to consider seeing a counselor.
Obsessions can spring up to protect the mind from lots of things - I would be guessing yours is probably grief over losing your husband. But usually there is more to it than just one thing.
By focusing on an obsession, your mind leaves you no room to focus on anything else, so that's why I say it is a protection (of sorts). It is just not a healthy protection.
A counselor or therapist should be able to help you worl through your feelings and get to the root of the obsession - and hopefully change it back into judst a healthy interest.