Rice Cereal in baby’s bottle

Okay so when my baby was 4 weeks old, his doctor diagnosed him with Acid Reflux & told me to put a teaspoon of rice per oz of formula in his bottle. He is 5 months now & I am still doing this. I honestly regret ever doing this. I feel like he didn’t Really need too but idk I just listened to the doctor. But anyways, Is it okay if I stop giving him the rice in his bottle? Or would that hurt his tummy? Lately he hasn’t been wanting to eat. He was eating 9oz bottles every 4 hours now he is only eating 9oz bottles twice daily.. it has me worried. He weighs 20lbs so I know he has to be hungry! Could it be the type of formula? Should I switch? Or should I stop with the rice? Thanks in advance. I am a FTM btw.