10 week old will not nap

Amanda
For the past week my 10 week old son will not sleep during the day.  He was taking an hour morning nap and a 3 hour afternoon nap and now he maybe sleeps 30 mins a day.  
He does sleep at night from 9-4, nurses and sleeps till 7-8.  I've tried nursing him to sleep, rocking in s dark room, putting him in the swing, keeping the house quiet and trying not to over stimulate him.  
He's still nursing every 2-3 hours, gaining weight fine and lots of wet and dirty diapers.  Any advice?!