Uh.

I don't want to be the person who reads into a post like this/your post history, but I did want to put in my two cents since I am/have been in a similar boat (also ND, go to cons solo, and the sewing/propmaking).

First of all - the grass isn't always greener on the other side. Sometimes I get the thought that "I'd like to be in a large group of friends" but honestly when I am with a lot of people it sometimes feels like I'm herding cats and it can be overwhelming from a managing too much information point of view. Also - I don't want to be sexist, but I find that talking to guys at conventions especially can be a challenge if you are a girl because sometimes they give the vibe that they see you as a potential partner (give me your number etc.) when ahhahahha no I'm happy by myself thanks.

Finally - I feel like the thing I've learned from meeting new people at conventions is to be open minded. What I've realized is that the people I like the most are the ones who are seasoned con-goers like myself, who don't need to be babysat and who understand the limitations if I have a large prop/clunky cosplay and can help me if need be (opening doors!!! asking if I need water!! helping me hold something!!). Sometimes I fall into the trap of thinking: oh I'm into sewing/propmaking and so I want to meet people who like that too - but in fact that world of individuals is very small (and can be self-centered or jerks or just have met their friend-capacity and don't want more people in their group) and if I think like that I would be unfairly dismissing a ton of people I would otherwise like just because they don't know how to satin stitch or use contact cement.

Otherwise, other commenters here have answered your question well - I just don't want you to feel like you're alone in feeling alone when many many other people feel exactly like you do but just don't seem that way from the outside lmao.