As a baby, your baby tends to sleep soundly anywhere, anywhere. This is because when a baby is asleep, there are no different stages of sleep that an older baby or an adult can experience. You can click over here to search for the baby sleep patterns introduced by the professionals' advisors.
Newborns spend most of their sleeping hours in deep sleep, making it difficult to wake them after a nap until they are ready to be replaced or fed. Now that your baby is older, they're starting to enter the world of adult sleep, which means they'll be on and off in different phases: deep sleep and active sleep, just like you.
The problem is, your baby doesn't know how to cope with this new sleep cycle. While rocking or feeding your baby to sleep, it may take a full thirty minutes to fall asleep completely, only your baby will wake up less than fifteen minutes later. This is because your baby has a startle reflex while asleep and wakes him up frequently.
If you can't sleep, find someone who can help: mom or dad. As if that wasn't stressful enough for you, your baby is actually sleeping soundly earlier in the night. The technical definition of "night sleep" after 4 months is a five hour portion.
Although he can sleep about five hours, he wakes up periodically during the night. Herein lies the challenge. Your baby is growing, the world is getting more interesting and he has to learn to fall asleep on his own.