Is there any cause for concern regarding a 5-month old baby, who sleeps 13+ hrs at night, and only stays awake about 2 hrs during the day before needing a nap (1/2 hr to 2 hrs long)? Also, baby is not rolling over yet, or showing signs of trying. Otherwise, he seems well, doesn t cry a lot, eats ok; he s just rather quiet (almost lethargic at times).