My 11 month old DS is very sleepy in the day?

[dejags]

DS2 has been so sleepy the past couple of days. He normally has one 2-3 hour nap in the middle of the day and has historically been an awful night time sleeper.

In the past couple of days he has been really tired in the day - today he woke at 6.45am, went back to bed at 8.15am, slept till 10.30 am and went back to bed at 12pm and is still sleeping (we are one hour ahead of UK time).

He has been tired and grumpy for a few days - I was wondering what it could be?

his night-time sleep is sporadic at the moment, last night was really bad but for the few nights preceding that not too awful.

I find my terrible nite sleeper sometimes goes through stages of sleeping more in the day, not sure if it is just catch up or not as it doesnt preceed illness or devel milestones as far as I can tell. Not much help but sounds very similar to my 10 month old.