Not Eating Constipation?

After ravenously devouring her veggies this morning an afternoon as usual, one of my piggies is suddenly acting lethargic and taking no interest in fresh foods. She seems like she might be bloated/constipated as I have not seen her poop since she started acting weird. She ate a few bites of hay but is mostly just sitting in the corner looking unhappy. I just moved to a new city (boston) and need to find a good vet in the area. If anyone has any insight as to what might be wrong and/or knows of a cavy savy vet in Boston please let me know!