What can I use to glue my tooth (not crown) back in? (Photo)

You have a "Maryland" Bridge which attaches to the back sides or top of the adjacent teeth.  Recementation of this type of bridge requires professional cementation by the dentist.  There is nothing you can place that back on with that will not cause issues or break free.  Hopefully this bridge can be recemented back in place with no issue.  You need to make sure that the teeth are healthy and decay free prior to cementing.Go see your dentist asap, you don't want the surrounding teeth to shift and cause the maryland bridge to no longer fit and this would wind up costing you more to replace.

Thanks for posting the photo of your bridge. Unfortunately this type of bridge has no over the counter type of cement. You will need to visit a dentist to have it rebounded. It's also important to determine why it came loose. It's possible you have decay present which caused it to fall out. Your dentist may be able to prescribe medication for your visit to help reduce your anxiety.