11 month old really sick

Hey, so my 11 month old little boy is really unwell he isn’t eating, drinking his milk, always screaming and crying. He won’t sit or play and doesn’t want carried but also doesn’t want to be put down. He isn’t sleeping and is really congested at night he’s really off balance even when he’s sitting up. When he cries it sounds like hes In pain but nothing makes him feel better he’s had 2 dirty nappies the last 5 days. I’m so worried about him. Has anyone experienced this?