I read online that a study was done and that only 22% of extreme premature babies were found to be alive between 18-45. i was born at 28 weeks with tourettes and adhd. does this mean i only have a 22% survival rate?

The "22% survival" refers to continuation of live birth after being delivered at a pre-mature state. If you are "18" at present, your lifespan is subject to other conditions than pre-maturity.

When you were born extreme prematurity was applied to those born at 24-25 weeks, not 28. There is a tremendous difference. I suggest you find a life coach/therapist to teach you stress management and relaxation skills. Your pre-occupation with death is not healthy.