It's normal to be scared, it's a big change, and it can be scary to think of the what ifs. But if you aren't truly living as you are and can't cope with the body you're in, you are, almost certainly, trans. Pretty much everyone has doubts or gets scared, it's normal.
Hormones aren't going to change who you are. Testosterone can make you a bit less emotional, or rather, change the way you feel it; a lot of people cry less or feel upset for a shorter amount of time than they used to. But that doesn't really have anything to do with your personality. It's like saying that having problems with controlling your anger is part of your personality. It's not, and it's not like meditating to be calmer makes you a different person, you know? You'll still be you, you'll just gradually look more masculine and you'll most likely feel happier with the body you're in or the life you're living.
I live in the UK too 🙂 where about are you from? And if you ever want to chat, just send me a message!