You can obfuscate your library, but you need to add all your public API as exceptions so Proguard won't touch it. It's a lot of work. Be prepared to test a lot.
Also, if you obfuscate your library, you'll usually want to either obfuscate its dependencies too, or add those dependencies to exceptions. In the former case, your customers won't be able to upgrade the dependencies without upgrading the entire library, in the latter the entire obfuscation will be weaker.
Of course even after you add everything, you may stumble on more problematic issues.