It does sound like you might need to get some kind of medical help alongside making some changes in your life. Maybe therapy? Meds are always an option, but if you were anxious at such a young age then you probably need some very in depth therapeutic work. Are these new friends people you will see again do you think?

Anxiety is really debilitating. I am going through quite a crisis right now because of it and the only thing I can think is good advice is to get as much support as you can in every way, positive people in your social life and family.. and medical professionals who will really listen and explore the options with you. I would also stay away from people who are not good for your health. I had almost no social contacts when I had to go into hospital three months ago. It took a while, but I have two girls I meet up with regularly now and maybe a third too.. It was scary to start because you wonder what people will think of you.. but eventually with effort you can build a small network of supportive people who will enjoy spending time with you. I started by texting a lot of people I knew through my Dutch course and these were the only two that kept in touch. It was terrifying to start, try to open up to people. But now I know it was worth it.

About the holiday.. If it could be a positive time for you then it is worth fighting through the anxiety to the good time on the other side. I find anxiety is always worse before doing something and once you get started it usually reduces or goes away completely. However if it is not something you actually want, then why put yourself through it when you can just cancel. In other words, do what you want and don't let the anxiety boss you around. And whether you go on this holiday or not, I really hope you do have one because it sounds to me like you could really use one! Maybe you can make the deal with yourself that you are going to have a holiday and then all you have to do is choose between Turkey or somewhere else. I think a change of scenery will give you a good boost