I had nail fungus on toes and fingers.
A general practitioner I saw said that I
shouldn't do anything because "many
people" get the condition, "nothing really
works," and I should just accept it.

Not likely.
Saw a foot-doctor. At my request she
prescribed
Pen-Lac, because it seemed to
have worked for me on a prior condition.
She also said Listerine and other
anti-plaque washes work: just swab the
infected area. Keeping the nails
cleaned and dry is supposed to help, but
now I doubt it. I think the fungus is
almost inescapable. Whether it comes from
old, moldy books, wet floors, old socks,
shoes, sweat, air, or whatever.
So I did both. I used Pen-Lac
religiously, cleaned the nails with
alcohol (
"hic!" 
).
I was told I could clean them every day,
or every few days; I don't know which
works better; and ocassionally swabbed
them with an anti-plaque.
The toe fungus is very nearly completely
gone.
The finger problem, not.
It looks like you have black streaks in
your nails, as do I. My toenails had no
black streaks but were yellowish and
brownish. So I must have two different
kinds of nail fungus, or which I have been
informed there are "four major
categories." So Pen-Lac doesn't always
work.
I have been cutting down my finger-nails,
the discolored section, a little less than
1/4 the entire nail area, in hopes that
exposing the skin

and then, if the
problem is with the skin underlying the
nail finding some way to treat it myself

,
and if it isn't the skin, I'm hoping once
the nail is removed far enough, when it
grows back, the problem won't.