Any advice girlies.....................

More related to those of you with older children but that forum looked fairly deserted and I know you lovely ladies won't mind me posting in here! DS is 4 and started reception class at the beginning of September. He was fine for the first fortnight, went to line up in the yard without a problem and went in and out of school with a huge smile on his face. Have to confess I felt a bit smug that he'd settled so well lol! Last week and today have well and truly wiped that smile from my face though. He cried every single day last week and had to be peeled off me this morning and taken in by his teacher. It's breaking my heart to see him like that cos he's usually such a happy chappy and quite confident for his age. I know he's fine when he's there as his teacher rings me and he's full of smiles and hugs at hometime. It is quite hard to get him to talk about what he's done at school but he was never that hot on volunteering info on what he'd been upto at nursery either, methinks toys and running around are more interesting than mummy! I've tried cuddles and talking to him, as has OH, about what's changed and all he says is that school's boring and too long. He used to do 2 hours a day longer at nursery, 3 days a week as I was working then so I don't understand that one. I've tried bribery (first with stickers, then with sweeties~desperate times = desperate measures!) and I tried being toughish this morning with the 'one kiss, one cuddle, now go and line up please' talk which obv didn't work! I just don't know where to go from here, nothing's changed at home, though I suppose OH is working away more as he's got a promotion at work but we can't change that and he was doing that before DS started school.
Please help a tearful mummy, any words of wisdom welcome and appreciated!
CB
Xx