Help want

Hi, this is the post that isn't about looking for job, but also need your help.

I just found a bounch of junk mail was send out from my email address at yahoo.com to everyone of my contact list. It is bag email, of cource.

What should I do? I changed my password now. But I am worried about to be send junk mail again from my email address. It is my email box for many years. I don't want to use new email address.