In a panic: New brown spot on my skin

I'm worried tonight: Do new dark brown, raised spots normally appear on people in their 30s? I thought benign spots were only a sign of aging.

I just discovered a new dark brown spot on my skin where there was none before. 

It seems to have appeared almost overnight, or at least grown very quickly. It looks symmetrical, mid to dark brown, about 5mm, and a bit raised.

It's in an area that isn't exposed to the sun. I'm very light-skinned and easily burn, so for most of my life I've stayed out of the sun.

I will get this checked by a doctor, of course, but I'm terribly frightened and to help me deal with this, I need to know whether I'm experiencing something common...

Also: I've had many moles over the years, but I don't remember new ones appearing until last year. I'm 36, and last year I noticed a similar spot on my face appear suddenly, specifically on my temple just behind the hairline. It's light brown, and also about 5mm. The dermatologist looked closely but isn't worried about that one.

I had my first baby in 2012, and I noticed skin changes happening after that. One skin-coloured growth on my face last year which later disappeared, the one I mentioned on my temple, and now this new one. 

Does anyone know if pregnancy triggers skin changes like this?

I'm feeling a whole new kind of fear, since a new brown spot isn't a symptom that can be imagined into existence by someone with health anxiety. It's really there, and it appeared out of nowhere. That's scary!  Does anyone else have experience with this?