My 22 month old son woke up throwing up what looks like old milk and after that yellow liquid and lately he haven't been eating right what is wrong?

Vomiting, not eating: If vomiting occurs, you will notice the content of the child's recent meal(s). When all the partially digested food has been vomited, you will normally see a yellow liquid, which is essentially stomach acid. This means that the stomach is empty. If the child is not keeping fluids down (continues to vomit) and/or the "yellow" liquid is now greenish in color, call your pediatrician.