R..
3 months is a growth spurt time... so he could very well be hungry. When I was working, my hubby had to feed our DD bottles of expressed milk. I always nursed before leaving, and usually left one extra bottle's worth of milk in the fridge just in case she needed it. (so if I was working a 6 hour shift, there would be 3 bottles in the fridge.)
I came home one day from a 6 hour shift, (when she was about 3 months...) and I had left 3 4-oz bottles in the fridge. My DD was absolutely ravenous when I got home! After a couple days of eating double what she normally did, she settled back down into eating her 'normal' amount again.