What has happened to you has also happened to many others across the globe. I suspect, from the tone of your message, that you would like some legal recourse. The legal authorities do have methods of tracing user identities from IP addresses. In the future, you should do this as soon as you have learned of the security compromise. At that time, you should also immediately change the passwords on all your accounts.
Some states have investigative services devoted specifically to Internet-related crimes.
If your reputation was harmed in some way or if derogatory information was said about you, you may have a stronger legal case. Remember that, when using the Internet, your privacy can never be guaranteed, so use it cautiously. When you use the internet, all companies want to identify their customers. The way that they do that is diverse and, the security that they employ is diverse. Some companies store your ID in a cookie on your PC and, it goes unencrypted over the net.