You can google or check NICE or NHS for official guidelines, but in brief:
Don't give anti-pyretics (paracetamol or ibuprofen) for a fever in isolation. A fever on its own is the body fighting an illness. It's a good thing, try and remember that.
Give either calpol or ibuprofen if he is in pain, discomfort or unwell. If whichever one you are giving doesn't work, swap to the other and if you are still worried, take medical advice and they may advise alternating and they may want to check him out. Don't routinely alternate them.
There is no temperature at which a child must have medical attention. Some dc cope well with high temps, some are very poorly with only a mild fever. Try and look at your child. How does he look? Is he still drinking and hydrated? Is he breathing normally now? No sucking in under the ribs or around the throat? No rash? No unusual drowsiness or inability to rouse? The numbers on a thermometer don't tell you anything concrete about how he actually is. Try and judge how he is based on everything else you have.
A fever can make a child miserable. Fluids or ice lollies help. Light, loose, cotton clothing and a sheet instead of a duvet/blanket. You want to aim for making him comfortable in gentle ways, not shocking his body so it shivers as this will raise the temperature which will make him feel unwell and tired. Air circulating can help so a crack of a window open but a comfortable not cold room. Or a fan on but not directly on him, just in the same room. Did they say what was causing the bug? Is it a cold or did they diagnose something else? Breathing problems associated with respiratory tract infections can be helped by steam (in the bathroom, shower on or kettle boiling in the room repeatedly or a damp towel on a radiator). And cold outside air can help too. Wrapped up, a quick walk outside can help the airways sometimes. But if you are concerned about breathing and it doesn't ease with things like propping up the cot, vicks on a rag tied to the bed, snufflebabe, steam, quick stroll outside, then seek further help.
Trust your instincts. You are his Mum. Any concerns, phone and chat to somebody on NHS direct (if you're in this country) or whatever is available.
It's so miserable seeing them poorly but chances are it will pass and he will bounce back quickly.
Have a sneaky hug too. Sounds like you need it.