over feeding??

Meghan
My LO is a month old and around 9lbs. We are mostly bottle feeding with breast milk and some formula. He will usually take 3oz every 2-3 hours during the day, and 4oz every 3.5-4.5 hours at night. The last few days he has been incredibly fussy during the day and acting like he is hungry just about every hour. We have upped his day feedings to 4oz, but I'm really worried about over feeding since we are using a bottle. Could this just be a growth spurt and the extra feeding is temporary? Do we just need to feed him more? When we burn him he doesn't spit up or anything. 
Edit: thanks everyone for responding! You all have made me feel much better!!