Chris, most of us has been where you are, take me for example... 9 blood tests, 3 ecgs, 3 trips to A&E, endoscopy, ct scan of chest abdomen and pelvic area, couldn't eat, sleep was all messed up, seen 6 different docs, had numerous physical examinations, yet i still think there is an undiagnosed disease at work in my body.
Ask most people here how many times they have been to hospital or doctors or had so many tests and they all come back clear, and i bet you that nearly everyone has.
We all have done this and we all have health anxiety, so logically speaking it's gotta be anxiety hasn't it?
You need to STOP READING UP ON MEDICAL STUFF!!
Ive been there and done it and so so many of us have and it doesn't help in the slightest because guess what? You don't have that disease and it's only your anxious mind telling you thast you do, you will need to learn to control that part of your brain, and i would suggest you go back to your doctor and have a heart to heart about your fears and he / she will advise you accordingly (most likely cbt or some kind of therapy)
On another note, i have noticed many vains and spider vains on my body than before because i notice my body so much more now and the fact i've lost 2 stone cuz of anxiety.
I don't mean to sound harsh, but mate u need to relax and try to think logical, i mean your 22 ffs, i'm 23, the chances of us having diseases at our ages are so slim in most cases