Hi H.,
My daughter did the same thing at that age; slept good the first half of the night, then woke for two or three feedings in the wee hours, and cat-napped all day long. Our doc said that was fine, and eventually (around 5-6 mos) she started consolidating her day-time naps. She was a frequent waker at night through 10 mos, though I stopped feeding her at night between 6-7 mos. One thing that helped her (and me!) was sleep training (training her to put herself to sleep). It made her sleep longer during naps and at night; I did sleep training between 3-4 mos, and continued the principles until she became a great sleeper on her own. I did a modified cry-out method, where I laid her down almost asleep, she would wake right up and cry, and I would return in 5 min to soothe, then started waiting longer. This method took longer than some others, but it felt right for both of us, and eventually I could put her down awake and she would go right to sleep on her own, with no fuss. There are tons of methods; having an older son you probably have experience in one or more. Some kids catnap, but he'll get all the sleep he needs, don't worry!