If you ever have issues of someone stealing your work this is what I was sent by Tumblr Support. Hope it helps.
If you are the copyright holder for the content that you are reporting, or their authorised representative, please complete the following DMCA notification form, located at https://www.tumblr.com/dmca
It’s definitely a problem. Pass it along.
Reblog if no matter if you have 50,000 or 50 followers, you appreciate every single one. Reblog if you appreciate the messages you get, whether it’s 100 or 1. Reblog if a little smile comes across your face everytime you see a new follower or message. Reblog if even though most of us aren’t tumblr famous, we appreciate the little things.
I don’t think you all realize how much I love you