4 month old not eating much?

Hayley • ~IT'S A GIRL!! 💕baby # 2 due May/June 2019~ 💙William Jack 17-08-17 💙

So my little boy has always loved his milk. He's mostly formula fed but I nurse him for comfort and the tiny bit of milk I still have about twice a day. So he's started napping every 3-4 hours every day which he didn't do before. Up until a week ago he barely napped at all. Since the napping his eating has gone way down. He just doesn't seem interested. He has maybe 2 full bottles a day and when we try to feed him the full 5 he only has about 1/4 or 1/2 of those. He seems generally happy, he's a very windy baby so he grizzles because of that sometimes but other than that seems fine. Still poos every second say and about 4 wet nappies a day. Is this just a phase? I thought it might be because of teething but gums look normal.