9 month old on eating strike

My now 9 month old baby has not received any solid food for 2 months now, despite the fact that when solids were first introduced, he could not get enough. He ate absolutely everything he was given, vegetables, fruits, infant cereal etc. Now the mere sight of as spoon in his direction sends him to a crying fit. He has now started to lose weight, and I am getting very concerned. Any ideas, I feel like I have tried everything????