2 Yr old Chronic Vomiting

My 26mth old has had horrible smelly watery stool since the end of August.  Vomiting episodes about on a weekly basis starting early in the AM hours, lasting for about 3 hours.  First vomit is a little food littered, then the remaining vomit is absolutly clear & thick.  Vomiting every 15mins like clockwork for 3 hours +-.   The stool got better in past week- much more solid and not as stinky.  We though we were done- until the vomiting recurred again today.  (that makes 4 weeks of at least one day of 3 hour vomiting)  She has lost 2 and 1/2 pounds since end of August (30lbs August 10th to 28lbs this last week)
No fever- except when very dehydrated.  VERY active child- very happy- eats extremely well and drinks fine.  (like any other toddler she has bad eating days and good) No family history of eating disorders or food allergies.
Blood & stool tests all negative for viruses, bacteria, liver & kidney function fine.  only concern is CRP levels very high (doctors assume it is swelling in digestive tract from vomit/diarreha?)
Waiting on food allergy blood work to come back, but not hopeful it will show anything.
It has really got us frustrated and worried.  But so long as all blood work is OK, should I really be worried?  I have a history of reflux, but i would vomit once or eat and be OK....  If this is reflux, why would not the symptoms abate after eating or drinking- and why does the vomiting come weekly for 3 hours or so and every 15 mins?  Any ideas i should have my doctor look into concidering blood panels come back OK (except for CRP levels)?