Baby eating less?

So my baby is 9 weeks old and is exclusively breastfed. The past two days he has only been eating from one breast for 10-15 minutes and then he will unlatch and either sleep or just be done eating. Then he won’t eat again for another hour to hour and a half. Before this he would eat from both breasts, about 20 minutes each minimum, and then eat again anywhere between an hour and a half to 3 hours. Does this seem normal or should I be concerned about his sudden change (decline?) in eating.