I am going through the exact same thing over here, April! If I don't hold Brady for his naps, they last about 15 minutes. The only other time I can get him to sleep is if I drive him in the car. I don't just go out to drive him, but I definitely plan my outings in the afternoon to get him to sleep. He's also been really fussy lately because he's so exhausted during the day.
I've tried pretending it's night time by swaddling him and putting him in his crib, but the little bugger seems to know I'm trying to trick him!
Hopefully more BTDT's will chime in with help.