3 mo.old change in schedule?

My 3 mo. old has put himself on a schedule for the past month. 2.5 hours between nursing, and nap about 1.5hours after each nursing. so about 4 naps a day (usually only 45min. - hour long). I've noticed, though, that he is no longer that hungry after 2.5 hours, and sometimes sleeps through his feeding time, so I'm trying to tweak his schedule so that he eats every 3 hours, and takes 3 longer naps. He's eating great at his feedings now, but sleeps less at each nap...now only 20 min. I'm going crazy. He wakes up from nap all happy, but if I were to take him out for a stroll, he would fall asleep again no problem....why are his naps getting shorter instead of longer? He's obviously still tired when he wakes up, otherwise, he woudn't fall back asleep on a stroll. could it be that my change in his schedule has thrown him off track?