Welcome sa community, mama! Nine months is still pretty normal for thumb-sucking kaya don't stress too much, karamihan ng babies do this para sa comfort, lalo na pag sleepy or overwhelmed sila. A few of us tried redirecting to a lovey or soft toy instead, or keeping baby's hands busy with safe toys, pero honestly most babies outgrow it naturally by 2-3 years, so for now focus lang sa ensuring it doesn't become a hard habit (like avoiding it during waking hours kung kaya mo) at least that helps later on.