Abdominal discomfort. Please help.

My 4 yr old boy was absolutely energetic and normal till yesterday afternoon. When having lunch, he started with complaining that his anal area is paining, and looked distressed. Within a span of 2hrs, he started running 103.5 fever. We connected with local peadtrician here and he prescribed calpol 250mg for fever, Decolic 2.5ml every 3-4hrs and Taxim O forte 2.5ml twice daily for 3 days. Currently, fever has reduced to around 100deg. However, he is having repeated stools which is transparent and watery - changing from lemon yellow colour yesterday to bright green today. He has been to potty 10-12times so far since yesterday afternoon to today afternoon. Zero appetite, very weak. Please suggest how to take it from here.. he has had 3 calpol doses , 4 decolic doses and 1 taxim o dose till now. He is also drinking ORS and water regularly and has had 1 dose of NexproJunior. Please help.