Ive had 1 cc total betamethasone injection in my jaw joints for tmj! is it too soon to get 1 more injection, as its already worn off?

3-4 months: Steroid injections should not be performed more often than every 4-6 weeks. If the effects are wearing off rapidly, injections might not be the best treatment option.

Don't know: How long has it been since your last steroid injection? Have you had your occlusion evaluated by an Orthodontist to see if malocclusion is causative/contributory to your joint dysfunction?

Depends: Depends on how long it's been. Frequent or many steroid injections in TMJ probably not a good idea.