Yesterday and today my little man isn't sleeping as he 'should'!!

Today especially... he has been up since 8am had a feed, change, play and tried to put him back to bed at around 9am. He wouldn't have it... he has only just gone into his own bed now and has been quiet for 20 mins but is still awake!!!!! He has only slept for about 1/2 hr from 8am when I had him in my arms. I have fed him again and changed him and given him some more play time. He is exhausted but wont sleep.

Any suggestions on how to get him to sleep??