Quoting Allissa Specht:" My ds is 4 months old today and for the past two weeks has refused to nap during the day! Seriously he ... [snip!] ... now, but he's always taken a couple naps during the fay. Is this just a phase? Will he outgrow it? Should I push naps more?"
He is most likely teething, my DD would sleep through the night at 2.5 months and took 2-3 steady naps a day and was in bed by 8:30 pm. When she started teething it disrupted her schedule to the point where she was up 3 or 4 times a night and took 1 nap if we were lucky.
Now if she is cutting cut, she still wakes up at least 2 times a night wimpers and goes back to sleep. Teething sucks.