Baby drinking way less than before?

My baby is 8 weeks on Friday. For his first 6-7 weeks of life he was insanely greedy. I exclusively pump so he drinks bottled breast milk. He always used to drink easily 4 Oz and sometimes want 5 or more. He would almost never turn milk down if you offered it as well! But the past week or so he’s been decreasing and decreasing daily. Now he will often not finish 3 Oz (90ml) and sometimes only 2 (50ml). He also seems sleepier. But when he’s awake he seems fine and normal really Should I be worried???