Otitis media 3 yrs old does it always need to be treated with antibiotics?

Depends: There are a few that are viral & settle down within a few days. They are more likely just to have a red drum & rapid onset. The ones with significant fluid or pus behind the drum that arise during congestion, colds, allergies etc are more often bacterial & might self heal in 4-6 weeks like they did in the 1800's (might not) the kid would remain symptomatic for much of that time. Best trust your doc.