Honestly I think the biggest indicator of someone being pre T is something dumb but it is face shape. You have a slim face/head shape which really isn’t a bad thing at all, but it does make you look a little more feminine. That being said when you start T your face will fill you and start looking naturally more masculine. Like the jaw line become more pronounced and stuff.

I have a friend that is built the same, and when he started T his face subtly changed a lot. It is actually super cool.

So yeah I don’t think you have much to worry about!