My Ancient Greek professor the other day told me that the plague in Athens wasn't the bubonic plague but actually another disease, if so, then what disease was it?
We don't know, although several possibilities have been suggested. Retrospective diagnosis of diseases and disorders in the ancient world are notoriously imprecise and conjectural--Claudius has been said to have had every disorder under the sun at some point, for example. Ancient authors were not able to observe many symptoms that modern medicine can, and ancient texts describe symptoms very differently--the Hippocratic Epidemics, for example, often focus on symptoms that modern doctors wouldn't necessarily pay as much attention to. Since many plagues have fairly similar symptoms (not to mention the fact that diseases and their observable symptoms will change over time) it's often not possible to get particularly specific with identification. Nor does it necessarily get us anywhere--in general it doesn't really change very much to know precisely what disease ravaged a city
You may be interested from this thread from a few months ago, when this very question was asked!