Onset/development of Stuttering... I need advice!

Onset/development of Stuttering... I need advice! Stuttering hasn't really ever been something I've had to deal with before... But lately in my life I have had a lot of stressors, and anxiety and depression have been a daily struggle for me, along with near-crippling headaches I get sometimes multiple times a day. A few months ago, I was surprised while reading some school material aloud before a huuuuge test (something I do when studying to help me remember it) that the word "deliver" was almost entirely impossible to say. Since then I've been able to avoid most conversations totally, and when I get overly stressed out I tend to just... Not talk. That may sound insane, but I'm 17, going through cyber school, my mother is almost never home, and when I go to my dad's all we do is sit and watch TV - silently, aside from laughter. But I do struggle when chastising my 3 year old sister, who I babysit constantly, with things like "-Don't- -do- that again" or "Sit in -time- out!" and such. (I've started substituting with things like "Stop" and "No") When I'm with my boyfriend (of 3 years) I don't seem to have a problem at all, though. I think it may be tied to stress, or anxiety, then? I don't know... Yesterday I had, sort of an 'interview' with someone to join an online D&D game, something I'd been planning for a while, and in an attempt to calm my anxiety beforehand (because things like that cause great anxiety for me, to the point if I think too much about it I get nauseous and often times I'll make up a reason to cancel) and clear my head, I meditated for half an hour. Then, the whole five-minute conversation, I was fine, i didn't stutter at all. But it's going to be unavoidable in the group sessions, which are PLANNED to be at least 4 hours long. And tomorrow he wants to start character building, so I really don't know how I'll get around it. God forbid he ask me to play a Tiefling, or a Dragonborn! But... It seems to be only the beginnings of words, and sometimes sentences? I can say "Seventeen" but not "Teen" on it's own without struggling. If someone asks where I live I can oftentimes say "Close to main street in Butler" but I can't just say "Butler" without struggling. Any advice?