Is there a maximum size limit for uploading to ArcGIS Online?
In what format is your data? Check the following technical article
42465 - Is there a feature limit in ArcGIS Online?
You could overcome the above limitation by publishing feature services from ArcMap to ArcGIS Online (AGOL).
ArcGIS Help (10.2, 10.2.1, and 10.2.2)
Also take care of the credits being used by AGOL.
ArcGIS Online | Service Credits
Retrieving data ...