My BMI

So I talk a lot of shit about the BMI system. So today I decided what my BMI is/was (I haven't weighted myself in like 2 months). Well it turns out that I am "normal" and that it is 20.1. Which is fine and whatever...but I am so unhealthy.
My issues
- HPV
- Teeth and gum disease(s)
- Heart Burn
- Depression
- (Maybe) Boarderline Personality Disorder
- Anxiety Disorder(S)
- High cholesterol
- Some kind of body temperture issue

Now that doesn't seem that good but my weight is fine--even though high cholesterol is associated with being overweight...weird!

I do read blogs about fit at any size...because I am small size but NOT FIT AT ALL!! What should I do??
- Start exercising
- Eat right
- Take care of my "medical issues"

That seems all great as I am writing this on the computer, but how the hell am I going to do that?? Especially since I don't know HOW to take care of my medical issues (well someone of them)!! WHATEVER