That's a very common pattern. Newborns sleep so much that when they come out of that phase, it's a disappointment!
Please don't ignore his cries. Infants need parenting to sleep for very good biological reasons. Most proponents of the 'cry it out' (CIO) method are absolutely NOT taking into account the current research that tells us what is normal and healthy for infant sleep. Here is a link to the world’s foremost expert on infant sleep:
http://www.naturalchild.org/james_mckenna/rethinking.html
that is just one page among many that will open your eyes to a whole new body of information that is actually evidence based, unlike cio, which is a culturally based method based on the parent’s needs rather than the infant’s physiological needs, as well as a misunderstanding about what is normal for infant sleep.
Harvard scientists have understood for years that babies should not be left to cry and try to tell parents why it is so important:
http://www.news.harvard.edu/gazette/1998/04.09/ChildrenNe...
And the knowledge that it is completely normal for babies to take a year or two or even more to develop the ability to sleep thru the night is not that new, either – it really makes you wonder why parents continue to ignore the information. Take a look at this article:
The Sleep Patterns of Normal Children, Armstrong KL, Quinn RA & Dadds MR. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retriev....
Medical Journal of Australia 1994 Aug 1;161(3):202-6.
“It is not until after 24 months that regular night waking (requiring attention) becomes much less common.”
The information about what is normal and healthy for infant sleep is so solid and compelling, that an entire country has drafted a policy against cio.
http://www.aaimhi.org/documents/position%20papers/control...
Why do parents continue to cling to and defend cio, when every shred of evidence we have shows it is inappropriate and does not meet the child’s needs? Our culture values independence strongly, and mistakenly believes that denying a child’s need for closeness will foster independence and confidence, when the opposite has been shown to be true.
It is also traditional in our culture to give priority to the needs of adults, regardless of the fact that imposing sleep training on infants is a practice that has been well studied and shown to be undesirable.
There are biologically appropriate, kind, evidence-based ways to deal with the normal sleep patterns of infants, but they continue to be ignored and dismissed by most parents in the U.S., where parents will insist that they cio for the children’s own good, despite the truth that we know better and have for years.
Elizabeth Pantley's "No Cry Sleep Solution" is one resource I know of that takes into account both your baby's biological needs and your own need for sleep. I recommend it highly.