What is wrong with my baby? He fights everything.

I understand that you're not medical professionals but I really don't think there's a medical reason for his behavior. For maybe the past two weeks he fights his bottles. It doesn't matter if it's breast milk or formula, he acts like he's hungry but doesn't eat much at a time. Now it's maybe 4 ounces when he used to drink 8oz right away in the morning or 6 after 3+ hours. It takes him forever to drink his bottle. He used to sleep through the night, now wakes up every 3-4 hours hungry. He's 6 months old. We started solids January 1st. He does 2 meals a day but is maybe eating a tablespoon, maybe two tablespoons of food each meal. This is my second baby but I don't remember my daughter acting like this. It has been two weeks of this nonsense. He's also extra crabby.