My baby stopped smiling 😔

Upon reaching 5months old, my baby doesn't smile anymore. He seldom cries and I tried handing him toys many times; but he isn't responsive. Sometimes, he looks at people watching him. Sometimes, he looks away. It makes me worried when I read this milestone. Actually, when he was 4months he smiled and giggled a lot. He grabbed his milk bottle often and good with his brothers. Now, I don't know what happened why he became like this. He has a scheduled check up with his pedia on Wednesday and it's making me anxious that I need some answers today...Does anyone here have the same case with mine? #5months #milestone #notsmiling #babyworry