EBV causes more severe symptoms the older you are. So everyone here who remembers getting it and it being terrible? That's because you got it as an adult. If you get it as a kid, it can be asymptomatic.

I got it at 36 and had a fever that leveled me for 3 weeks. Between "wait 1 week before bothering your doctor" and multiple rounds of tests, they didn't even diagnose it as EBV until the 3rd week.