You use the verb 'help' with or without a 'to infinitive'. Meaning remains the same.

You don't help yourself but you help others. Your third sentence sounds like you're helping yourself in maintaining the library.

I'm helping _ in maintaining the library. You don't fill in that blank. The object of help could be anything but you.

You use the verb 'help' with or without a 'to infinitive'. The meaning remains the same.

You don't help yourself but you help others. Your third sentence sounds like you're helping yourself in maintaining the library.

I'm helping _ in maintaining the library. You don't fill in that blank. The object of help could be anything but you.