The symptoms which you are telling needs examination by pediatrician
.It might be Viral illness.
But the posibilities of following illnesses should be kept in mind
with headache, meningitis
2.Fever with headache with abdominal pain;dengue
3.Fever with abdominal pain,acute abdomen
These all diagnosis should be kept in mind as per symptoms and needs clinical evaluation by pediatrician to rule out these illnesses.
Wishing good health for your baby