I'm fifteen, I had my last period when I was thirteen. Four or five overall. It's been long enough to warrant confusion. I am around 95-100 pounds and 5' even, have never participated in any sort of sexual activity, don't exercise outside of PE, I'm not stressed, I don't have any health problems I know of outside of poor eyesight, I'm not and haven't been on any medication or drugs. I am ten minutes of internet browsing familiar with the term secondary amenorrhea, and I want a second opinion. It's been over a year, what's goin' on.
I have told my mother, and as I am not bent double with excruciating pain, or any pain at all, she's not concerned. She did however say that if I felt I needed to we would go to a doctor, but I should know I would be on a medical table with my rear in the air pant less should that happen. I think she is full of it, mainly because unless it's pretty serious that is not done under the age of 21.

Do I need to see a doctor and have the oh so horrific scene above enacted? Or am I a 'sarcastic bag of mood swings and hormones'? Is this even in the right category?

your mother should be ashamed of her self. Yes a doctor ( and there are women doctors) may have to have you put on a examine gown. And yes they may have to have you lay or sit on exam table and look. They may also take blood samples, do a pap smear and maybe even a x-ray or cat scan.

Your mother should be concerned about your health, not trying to give you fear of having female problems checked. Her attitude is disgusting.

Next with that said, stop trying to be a doctor, there are perhaps 100s of possible reasons and people always pick the worst to think about. Most likely a hormone issue. It is not uncommon for girls, esp those that are somewhat underweight, and not very active, to be late getting regular periods. And some girls never get regular ones.

But a doctor exam is never ( never) a bad idea.

Considering your weight, it is not uncommon for you not to have a period. At your age this is not uncommon.

You won't need to have your rear "up in the air." These exams are for sexually active girls. A blood test to determine hormone levels isn't a bad idea though.