have you tried an app like Onsen? it's an AI personal assistant for supporting mental health. You can just chat away at it like having a free therapist and as its on your phone you can take it anywhere like a little cheerleader. I sound like a commercial. I have no affiliations i just found it helpful during eating disorder recovery.Recently I've installed an app called "skillsta" that's supposed to help with social skills/confidence and such.
Although you didn't find people your own age at volunteering did you enjoy it? You haven't told us what the volunteering was. I'd love to hear about it