So, I am just like you. 18, male, mild stutter among friends, strong stutter with parents or teachers etc. I HAVE been to speech therapy a few years ago, however I stopped because it stressed me out. Since then, I sort of made my way through life/school. I assume you are living in the US, which is why me giving advice (as a German) is basically useless. BUT: I can tell you this, if you have the time and are willing to put in the work, speech therapy might be perfect for you. Try it out for a few months, and then see what has happened. Still, I'd recommend visiting a psychologist first because stuttering often has a sort of "underground" reason