Just quickly sharing a link today. When R was about a week old he started sleeping pretty long stretches at night, like 6-9 hours. I thought "I must have the most WONDERFUL baby, by 6 months old he will be sleeping at least 10 hours consistently! This isn't so hard!" When R was 1 day short of 3 months old he rolled over from his back to his belly. For a week or so he slept terribly. Then he kind of got back to sleeping pretty well, as long as I let him sleep on his belly. His pediatrician said as long as he was big enough to get himself to his belly if he rolled over in the night he should be fine. Then, right at 4 months old he started sleeping TERRIBLY! He was waking up every 2 to 3 hours at night, did NOT want to take a nap, he even completely gave up his binky because he figured out when he sucked it he fell asleep! He started hating to be rocked and would flail while he was nursing if he got drowsy. I was panicked! I asked around to some of my online Mom groups and heard a term I had never heard before "the 4 month sleep regression". I thought, "how have I never heard of this, I have read so much?!" R is now a little over 5 months old and we are still having restless nights, but he is napping better most days. Some nights he sleeps for 6 hours, some he is up every 2. I think it is a combination of being to busy during the day to REALLY eat and his mind being too busy to really rest at night along with some growing pains and teething pains. Hopefully he grows out of it soon, if not, we will all survive I'm sure!
This link shares some awesome information about the "4 month sleep regression" idea.
KellyMom has lots of great articles and resources for all sorts of other baby topics as well!