Helpppp

Basically I need to make a doctors appointment about how I feel (I’m feeling really lost and lonely, worthless and so so unhappy, also I’m suffering with really bad anxiety every time I go out of the door). I was just wondering if anyone knows how I can explain that in a way that my doctor actually listens. I feel really embarrassed talking about it and I mix my words up a lot. So if anyone knows any advice on how to speak to them about it then please let me know! (I’m 18 and live in the UK)