OK after messing around with all eclipse files and stuff, I found the solution:
I had to use a new workspace that wasn't in the parent folder of the current workspace, explanation:
Old workspace:
somefolder/parentfolder/workspace/
Every workspace in the parentfolder/ is corrupted, so each time I was trying a new workspace in this folder, it didn't work
By using this kind of workspace, the problem wasn't there anymore:
somefolder/workspace
My advice to you if this happens: do not only use the parent folder to try a workspace but a completely random other folder.
Hope this helps other people in the same position.