Either your four-month-old baby has suddenly grown up, or it should be shown to your pediatrician, to whom your four-month-old baby is probably attached. Here everyone will be advised, and you have one child of four months.
Good afternoon, Victoria! It is difficult to answer your question unambiguously without seeing the child, but sweating can be, for example, with rickets. Therefore, you should contact a pediatrician for an in-person consultation, then the doctor will be able to give recommendations.