so my son has been latching on since last night and whenever I try to move him to the other side he…

so my son has been latching on since last night and whenever I try to move him to the other side he stops taking it. Sort of like he gets lazy and doesn't want to work for it and just wants the bottle so what do I do? How do I get him to latch both sides in one feeding? I ask because my milk supply is trying to dry up and I know with him latching it will increase but he needs to latch to both sides right?