Antibiotics can take upto 48 hours to show effect. The fever decreasing in frequency is a good sign. Continue the antibiotics and ensure medication you're giving medication to decrease the fever and keep child hydrated with plenty of fluids. In case fever is not reducing or increasing, antibiotics may need to be revised and child will have to be checked clinically to see if the infection is going down.

Didn't mention the age and weight. If he had fever on Saturday morning and came in every 6 hours then very likely it was viral fever. In that fever comes in every 6 hours and will be there for 3 days so as it started on Saturday morning it can be there till Monday (ie today). If it continues Tuesday evening then need to go for reports. Mostly being a viral, give medicine for symptomatic care. Don't start antibiotics for the better health of your child.