Hi Baz,
You probably have fallen victim to a successful phishing attack that has acquired your email address and password, and utilized that to gain your contacts list. The phishing attacker uses financial or social engineering language for example "Click
here to see who is searching for you on Google". Subsequent spam to your contacts appear to be from you, but a check of the email header would indicate that the originating IP is not a Microsoft/Yahoo/Google address. I don’t believe there
is a solution to this. The moral of the story is to never disclose your credentials unless you are sure you are speaking to the true authority.
Doug