I know exactly what u mean, I suffer with the same thing! Since I was about 11 years old I couldn't stay over my friends for a sleepover without worrying about/being sick. This gradually got better as I got older and I was able to stay out for a night. However I still struggle with going away from home for a period of time, or being too far away. I'm just about to go away for a week with my boyfriend, the first time I've gone on holiday without parents! I'm much better than I have been previously though, not so anxious, but getting symptoms now and again! Have u tried therapy or anything?