Hello girls, I have such a problem, we're about two months in but the …

Hello girls, I have such a problem, we're about two months in but the baby is constantly asking for formula every hour, he cries really hard, I give him every 3-4 hours, 3 bottles of 90ml each. I also breastfeed him. Is this normal? I'm just worried because he's still small. My milk supply is low because of that, so I'm giving him formula.