I have Lightroom 5, I've been using it for well over a year. When I opened it last week, it acted like it was a new install and I was opening it for the first time, it asked me to choose my country and to choose a location for my new catalog. Once I did that it removed my old catalog along with a LOT of pictures that we in it and it appears to have reverted back to a previous version of LR, all my controls appear to be LR4 instead of 5. Anyone have any advice? Should I just uninstall and start over?
Seems unlikely that your old catalog was removed. More likely that a new empty one was created and switched to.
Check your menu /file/open-recent/ to see if your old catalog is listed.
If not, use your OS tools (Finder or Explorer) to search for all the *.LRCAT files on your hard drive(s).