J.M.
I didn't even begin to hope my kids would start to sleep through the night until the six month mark. My oldest son started sleeping through the night right about six months. One of my twins started at about that age (probably closer to seven months) and the other twin went to about eight months. I think four months is a little early to expect a baby to sleep through the night. How is it that he is taking cat naps throughout the day? Are you running errands all day and his crashes in the car seat? Or does he conk out with no warning and no notice. The difference I noticed between my oldest and my twins was that I really worked around my oldest's schedule but I didn't have that same luxury with my twins. I worked harder to accommodate the twins to MY schedule, which was like a hamster running in a wheel. (I was working really, really hard, but not getting anywhere.) They would fall asleep in the car when I was running errands. They'd doze off in their swings while I was preparing meals, etc. So they were "cat napping" all day, and not really getting a good rest. Then, they would cat nap at night. Once I recognized this, I made more of an effort to pay attention to their cues and work around what they needed. I found that they liked a nap in their cribs in the morning (long for one, short for the other) and they liked a nap in their cribs in the afternoon (fairly short for both). They worked wonders. They started going down at 7:30 p.m. I changed them and gave them a couple of ounces of milk at about midnight (right before I went to bed) and put them both back down. They'd sleep until about 8 a.m. - and I got my sanity back!