Baby weight slowed down. Consume milk?

My baby weight used to increase by 40gms per day... but now since she is 3 nd hlf month old her weight has slowed down alot.... in three weeks time it hasnt increased even by 10gms.... 3 weeks back when i checked it was 4.95kg and today its been three weeks its still the same 4.95kg... why isnt her weight increasing?? Usually it increases by 10gms per day right?? It hasnt even increased by 5 gms or 10gms it still the same..... also she has been feeding less for her age.... her birth weight 2.20kg... she is an IUGR baby.... has laryngomalacia.... although she is active and happy.. but i m concerned how will she grow if she doesnt consume milk?? I have been finding the solution for this from last month... but no one could identify the problem....