When i wake up in the morning, i have a weird sensation in my upper teeth (in the back). i don't think they are numb but they just feel odd. any idea?

Idea? yes: But suggest you see a dentist to find out for sure. Could range from bruxism to something serious. Find out for sure. This requires a personal clinical exam and x-rays.

Nocturnal Bruxism: also called night time clenching, may cause tooth wear, and even damage or break teeth. Currently, no therapy has been proven effective in treating sleep bruxism. See your dentist for night guard fabrication for teeth protection. Good luck.