It sounds like teething or a growth spurt to me. When he wakes at night, is it clear that he's hungry? Did you try PU/PD or another way to soothe him back to sleep without eating? I wouldn't change anything for right now, he's still young enough that it's important that he fill up on breastmilk, not solids. Variations in appetite are normal, so your best bet is to stick with the way things are for now and try to ride it out. Keep us posted!