The elastics we give patients, with instructions on how to put them in and take them out themselves, are an aid to moving the teeth alongside braces and aligners. When we hook an elastic onto braces, as well as movement in the desired direction we can also get side effects, such as the teeth concerned rotating or being pulled outwards (extruded). To minimise these side effects, elastics are worn when the archwires are a suitably large size and the teeth the elastic is hooked onto are held firmly by the archwire; alternatively, the elastic can be hooked onto an extra hook instead of a bracket. Of course, depending on why elastics are needed, there are also cases where they are started right at the beginning of treatment with braces, while the archwires are still thin.
This answer is for general information. Your own case needs an examination by an orthodontist.