(((Big Hugs)))
I have also been T1 since I was 3 and I am also the only one, and it has been rough sometimes, kids can be cruel, teenagers can be malicious, adults can be dismissive, and feeling at odds with yourself makes it harder to find a group to fit in with ( i know how desperately I wanted to fit in), and all the while having to manage the big D, all that responsibility and worry can make you feel older than your years and peers. I think at the same age I felt burnt out too.
Talking helps. Talk to whoever you can about how you’re feeling, us at Tu, your doctor, a counsellor, your family. See about getting something to help with the depression, there are plenty of medications that can just take the edge of the bleakness that you’re feeling, which is a start to getting back on track.
Try not to worry about the future (easier said than done I know, but I have been in a similar position to you), No-one knows what tomorrow will bring. Live for today, love, companionship, friendship is often found in the unlikeliest of places and when you’re least expecting it, (I found my greatest friend completely by accident 4 years ago.)
Do one thing everyday, that is just for you, for example paint your nails, or read a favourite book or sign up for something you always wanted to try etc because you are worth it.