gizmo.ella
Junior Guinea Pig


So 100g in three weeks or so... How old is he?
Definitely male?
They do hit a growth spurt at that age and get a fuller figure.
If you're unsure that Gizmo is a boy then you'll need to go back to the pet shop or the vet for him to be sexed.
Otherwise "he" might end up putting on a lot of weight if he's actually a girl and pregnant.
Can you post a photo of his genitals? Then we can give you the benefit of our experience!