Not sure what to do or how to calm myself to not worry

Hi guys,

Sorry this is a selfish post about me worrying I have something like cancer, when I know a lot of you do actually have this, so apologises. 

I have been refered to an ENT by my thyroid specialist as she believes the pain in my throats, the sensation of feeling something is stuck and the problem of struggling to breathe is an "inside" throats issue not an "outside" throats issue like the thyroid.

Basically, I'm only 19 and the words endoscopy, cancer really terrify me. I did the stupid thing of looking on the internet and stressed myself to the point I thought I had 3different problems. My friends mum who's a doctor, recommended me to talk on here to put down my feelings. 

I feel like I'm an invalid to my family, as I don't work, I'm in a lot of pain, I've been to A&E 5times due to severe chest pains and strangling sensation, but the issue is I feel like I'm making my symptoms up or that no one believes me because all the test results come back clear and don't get me wrong that is great but when you feel as rubbish as I do and you get told you're fine, it destroys you because you just give up.

If anyone has any advice or wants to tell me to suck it up and deal with it please be my guest. I hope anyone who reads this who's struggling with cancer or with someone who has it doesn't think badly of me for writing down my concerns and don't think I'm being selfish.

Thank you