Loose teeth after week 2 with Invisalign tray, what could be wrong?

My back teeth, especially the ones I chew with are very loose and I have already exceeded week 2 with my Invisalign tray. I can feel them move when I floss. Sometimes I leave my trays out for 2-4 hrs but, never exceed leaving them out more than 4 hours a day as I only eat once or twice a day. I didn't think I was doing anything wrong. There's nothing on the Invisalign instructions that tell you how long at a time to leave the trays out, just not more than 4 hours a day. What damage have I done?