Baby not taking feed. Any infection?

Hi, My baby is 54 days old, he is on breast milk and formula, but we feed him through bottle, as he spills out milk from katori chamcha, he has been taking feeds well till yesterday, since last not he is not taking feeds but sleeping a lot, when we try to keep bottle he sucks a bit and then cries and pushes away the bottle, it's been happening since last night, he has bit cold too, where he sneezing we did give him drops for cold, he is not taking feeds keep mouthing his hands in. Mouth, I am very tensed as he is not taking feeds, what could be there reason, any infection?, what signs should I check for infection, he is passing urine normally, struggling to poop since morning but unable to poop,(he poops every day), please guide and help, will take him to doctor by evening.