Why would a friend do this to you?

Well "nearly lovers" doesn't mean anything. If you two are simply friends then you have no say in where he sits, etc. Clearly something is bugging him....maybe you act like you are a couple without actually being a couple (like being somewhat possessive of him) and he is just fed up. It is crazy to be "nearly lovers" for 14 years! You are either friends or lovers....not somewhere in between.