On re-installing Ubuntu use option "Upgrade" to not wipe all home directories. You may then have created a new account rather than using the existing one. In case your file system was not encrypted your data may still be present in the home directory of your previous user. To test this open Nautilus and point it to "File System ->
/home. See what directories are there.
If your old HOME does exist you can point your new user account to this directory by installing gnome-system-tools and run Users & Gropus as was further elaborated in this question:
After Unlock settings with your administrator credentials you may from "Advanced Settings" change the location of a users's home directory:
Choose the directory of your old user account to recover all your data there.
In case your installation did overwrite your previous data you may be able to recover those data that have not been overwritten yet. See the following: