2nd dermatologist visit

Well did the doctor diagnose it as alopecia/hair loss?

The first time I went to a dermatologist about this, I had been obsessively researching it and it was obvious that I was experiencing hair loss; I didn't want it to be true but I knew it was, so I made an appointment with a dermatologist to get a prescription for Finasteride.

She ended up telling me what you're saying: that I had seborrheic dermatitis and I should use Nizoral shampoo and apply some other stuff to my scalp. I had already considered that maybe I was losing hair due to that, but read that nobody really loses hair to seborrheic dermatitis unless they're scratching their head so badly they're basically pulling hairs out. Which I of course wasn't, and you're probably not either. So basically, that dermatologist I went to was clueless and useless when it came to hairloss.

I went to another one and he agreed that her diagnosis was silly. He gave me a prescription for Finasteride and recommended Rogaine (or generic minoxidil).

Don't know how much you know about this stuff but there are really only 3 treatments you should be considering, in order of importance, but preferably all 3:

Finasteride/Propecia (best thing for stopping further hairloss)
Rogaine/Minoxidil (will regrow some hair)
Nizoral shampoo (helps a little in prevention of hairloss)

But basically, you should do these things:

1.) Find another dermatologist. Try to find out if they're experienced in treating hairloss, either by searching online or asking their receptionist.
2.) Make sure they actually diagnose it as androgenetic alopecia so you know it's that and not just telogen effluvium (which is due to stress)
3.) Read about Finasteride/Propecia and its side effects and think real hard about whether it's worth it to you.
4.) Get a blood test before starting Finasteride in case you end up having problems with it later. If your doctor tells you it's not necessary, ask for it anyway; my doctor said it wasn't necessary, but he also said he'd never had patient who'd had problems on it so he didn't think I would either, and he was wrong about that

But that's basically how it works these days.

Good post RU58841.
When I have any kind of health issue, I always try to consult at least two doctors. If their diagnosis is the same, I proceed with the treatment. If it differs, I visit another doctor to confirm one of the diagnosis set.
Confirm your diagnosis and if it is really hair loss then Finasteride is what you need. Actually I've heard that the "Big 3" (Finasteride+Rogaine+Nizoral) works good, however I use only generic finasteride.

I think you have to take your time and do some research about it and get opinion from the experience people...