Mine is exactly the same - would eat from morning until night. She's between the 50th and 75th centiles for height and weight. She's at nursery full time, has breakfast at home, then breakfast at nursery, then snack, lunch, tea and then a small dinner at home, then a snack before bed.
If she is actually hungry, she'll eat fruit or cheese or cold meat and crackers, otherwise she just wants sweet stuff which we limit. And she does stop when she's full - I think she just has a small tummy so prefers to eat little and often. Also, she never stops moving - even if I try to get her to sit still with tv while I cook dinner, she's jiggling around, hanging upside down in the sofa, dancing around in front of the tv.
Sometimes I do think it's boredom, in which case she gets water or milk offered. But She also does get hangry - I notice her behaviour gets much worse if I don't feed her on time!
And when it's really full on, it seems that a few days later, all her trousers and T-shirts are too short, so I do think sometimes it's a growth spurt.
No advice, just wanted you to know, you're not alone!