My two-month old feeding pattern suddenly changed, now wants to eat less more often. Formula fed.?

Was eating on demand about 3-3.5oz every 2-4hrs since one month, he was a calm quiet baby, slept a lot & basically cried if sleepy/hungry. Then past 10 days he's been really irregular. He's much more alert (good), but fussy & crying a lot before falling asleep. However he manages to sleep 5-6 hr stretches at night, now. But wants to eat very small serving,anywhere from .5 to 2 ounces at a time, as often as every hour. I know babies cluster feed during the day to make it through the night, but something doesn't seem right. I exhaust every other possibility (pacifier to satisfy his sucking need, holding, diaper, nap, reading, singing, playing, walks) & only eating works. I've monitored eating & its at least 4-5 ounces less than before, not sure since I didn't really monitor before since no problem. Doctor doesn't seem concerned since he's growing (saw him 4 days ago), but this problem was relatively recent & she blew me off. We're military & shes not my reg Ped. Any thoughts or exp?