6 month old refusing to eat

He doesn’t finish his bottles often, he eats 180ml. But normally it will only be like 150ml. He refuses his rice cereal and it is getting frustrating as I’m worried about his health. When I try to feed him more he gets upset starts crying, he eats maybe 20ml at a time and has to take a break in between, it’s hard because he also throws up a bit, he always has. But our doctor says it’s normal. He’s supposed to be hitting a growth spurt so I am worried:(