It's been 2 weeks since I had Neograft FUE hair transplant. What should my sleeping position be?

It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen.  In general you can sleep any way you like after two weeks.

For the first few days after surgery I recommend sleeping as upright as possible. This will reduce the swelling. After a few days (3-5 days) the swelling will have subsided and sleeping upright can help but as long as your not sleeping prone (on your face and grafts). Hope that helps!