Will speech therapy be effective for a 16 year old?

(North Carolina)

So I’m 16, in high school and I still have problems saying certain words or pronuncing certain letters (Been like that since I was young). This has always been an insecurity of mine and I want to learn how to speak properly. This problem prevent me from being comfortable in social situations or public speaking or anything that requires communication b/c I’m embarrassed about it.

So the question is will speech therapy work for someone my age and how long would it take?