Are online lectures protected under copyright?

Hi! I have produced and published an online class that seems to have been copied by someone for his Udemy course. He produced everything new, so it is not actually my recording, but the scripts, the slides and the new recording are identical in content to mine. The slides are actually made a little bit more cheaply, but scripts and slide contents are nevertheless the same. What should I do about this? I assume my own lectures are copyright-protected (but they are not registered as copyright) -- but does that help me if someone makes everything new, however identical in content?