Baby not growing

Hi mummies, when i did my last check up at 29 weeks, my baby was 1.6kg, and 2.5kg at 33 weeks Now that i checked again, baby is only 2.6kg at 35 weeks. He was always on the bigger side during the last few check ups but now he is just average. He has been kicking alot lesser too. Has this happened to anyone? Doc said to observe these few days but im very worried