What's wrong with the baby? The baby is 7 months old and I don't know …

What's wrong with the baby? The baby is 7 months old and I don't know what he wants, he's always crying, unhappy. I try to pick him up but he doesn't like it, he doesn't want to lie down either, he doesn't want to sit either. He's not hungry, I give him to drink but it's not right. Nothing broken, we don't hit or scold him but damn, I don't know what he needs ? He hasn't pooped for 3-4 days maybe because of that? But it's okay He has already got 4 teeth I smear Kamistad on him just in case