Breastfeeding Question- One Or Both Sides?

Satori

So my son is 3.5 months old and exclusively breastfed. Until recently, I’ve always fed him about 5 minutes on each side at each session. In the last week, he has not been wanting the second breast at all, ending the feed when I try to switch him. Is it okay to only nurse on one breast at each session? Will my supply drop if I’m not emptying both breasts and instead only emptying one every 2-4 hours?

TIA!