Overlaping medications *urgent*

My 18 month old has had a pretty high fever for a few days now. We went to the doctors and he said it's most likely a virus- amoxicillin was prescribed. I know fevers are technically a good thing, but we're talking 101+ fevers.. so doctor suggested advil because the pain/fever relief is better. Problem is, an 8hr dose is only lasting 5/6hrs. During the day I don't mind sticking it out- but it's so hard to watch him toss/turn in pain at night because I know how sleep deprived and sick he feels. My question is, can I give him tylenol after the advil has worn off and kinda alternate between the two? I'll probably be bringing him into the hospital if this persists.. i'm just waiting to see if the antibiotics do anything for him. TIA!