Can you offer some advice? My 23month son (I ha...

Can you offer some advice? My 23month son (I have a 4yr old girl)sleeps well at night usually goes to bed at 8pm and wakes around 6-6.30/7.00(some days). He goes down for a day sleep around 12.30-1.30 for at least 1 1/2hrs. He doesn't complain going to bed he justs know its bedtime and that's it.But for the last say 6 weeks around 9.30am he gets exceptionally whingey and crys alot, no diversions to take his mind off things works except sitting down for a cuddle with mum and this can be on going for 2hrs, he then perks up and makes it throught til his sleep.He has had a sleep at 10am somedays if in the car and then he won't have big sleep at lunch by 4-5pm he is beside himself. Great natured boy as a rule but this is sending me berko!! any one have any ideas please. KH9991