Suggest Medication For Fever Followed By Stomach Pain, Head Ache & Sore Throat

I have a 6 year old son who has been running a fever the last few days and has been complaining of a tummy ache, headache, & sore throat. He has been tested for strep and it was negative. Today his tummy ache got worse and when he went to the bathroom he had some diarhea. He also had about 1-2 Tbls of blood in the toilet. I have a call into his doctor, but am wondering what this could mean.