X-ray is the only way to be sure. If you can afford it and are stil worried then its good for peace of mind- or to catch it early if your right.
Antibiotics can sometimes take 3 days before you start to see a real diference. I wish they would give out more IV for the little 1s- even a loading dose then liquid at home. Here they give out IV all the time because kids die from the sicknesses, also you can request it if you think your kids weak/ had it before etc.
I would keep a close eye on your child and any change for the worse go straight to hospital.
BUT I hope your both doing better today