Is this mold on my bathroom ceiling?
Looks like some surface mildew. That's pretty common in a high humidity area like a bathroom. Blot the stains with some equal parts of water and bleach on a rag, followed by blotting with a plain water rag and let it dry. If you still see it, repeat the process. The bleach will kill the mildew and help to remove any staining left behind. If you still have some staining, a temporary fix would be some spray Kilz.

I would consider repainting that ceiling with some mildew-resistant paint.