Is it only recent? How long has he refused to drink? Sometimes babies would go on milk strikes for a few days then back to normal after. As long as the overall input over a long period (a few weeks or month) is good, a few days dip shouldn't be too big a problem.
Now he is back to normal he is refusing like playing with his milk 2 days a go and I also worried as he poops every 3 days .
https://sg.theasianparent.com/baby-development-2-month-old https://sg.theasianparent.com/breastfeeding-tips-for-new-mothers
W.