Moaning I have come on with a similar issue...
Dd sick Thursday night at 10.30pm. Said she had a sore tummy, throughout the day she has said she needed a poo and when she went to the loo nothing came out. She has poo'd though so she isn't constipated.
On Friday she woke up bright as a button. At breakfast and lunch then early evening started to feel unwell again, complained of a sore tummy. Wasn't sick though.
On Saturday she woke and seemed fine. Said tummy wasn't sore anymore. She had breakfast then we went out to do food shopping and for lunch. She are some lunch then started to complian that she has a sore tummy, needed to poo but then couldn't etc so we went home. She lay on the couch and seemed quite miserable but perked up a bit after doing a poo.
On Sunday, she was again fine in the morninf, at breakfast and lunch but was sick again late afternoon after being at the park. She was then sick again in the evening. So there was a gap between thur night and last night without her being actually sick 
This morning she seemed fine, asked if she was allowed cereal as she was hungry. Was playing around all morninf, fill of her usual nonsense and I thought that was her hopefully on the mend, but no, she had a sore tummy from lunchtime and was crying with it. Kept going into the loo to be sick but nothing would come up, or to do a poo but nothing came out.
She has eventually been sick today and said it helped her tummy feel better.
I'm just wondering if this is normal for big gaps in the sickness?
I have called our gp and am waiting on them calling me back. Dd has fallen asleep just now but is just not well at all 