Hi, hobansgirl
Welcome to the forums !
Until Ray gets back to you I can only mention that perhaps you should play it safe and change your password. Also check your other security information (security question, back-up email address, etc.) to be sure they haven't been altered.
FWIW, I'm not sure much can be done after the fact. Once someone has a contact list, he/she really doesn't need to keep accessing your account. They can simply copy the list for use at their own location and 'spoof' your (and others') addresses.
Ray and/or Big Dan may chime in with much more helpful advice for you !