Cat Napping 5 Month Old Son?

My son normally goes down between 9:30pm-10:30pm and he will normally sleep until 7, sometimes an hour longer sometimes an hour shorter but generally he's a 7am waker. Anyways, my question is he used to take a 1-2 hour nap in the morning, a 2-3 hour nap in the afternoon and an hour nap at night, but the last week or two he has been napping horribly, he's not following the same schedule we have been for months, and he's barely sleeping 30 minutes each name, what's going on with him? Is this normal, someday's he's not getting enough sleep and he's so fussy and cranky.