What does having white gums around and below my teeth mean? Nothing seems to have changed in my health or diet.

Maybe nothing. Your gums immediately below your teeth should be pink but certainly more pale than the mucosa further from your teeth. Gums are covered with a keratin layer, like skin, hair, fingernails. Mucosa doesn't have this keratin layer & is more translucent. Extremely pale gums could be a sign of systemic conditions such as anemia. I suggest you see your dentist or periodontist.
How White? If u r just noticing that there seems to be a pale pink band of gum tissue and then it gets dkr. Pink, that's perfectly normal. The pale pnk tiss contains keratin fibers that attach to the bone underneath and is healthy. If this band is extremely pale or almost tannish or beige, could mean u r dehydrated - see ur md. Anything else and i would advise a visit to the dentist or hygienist to have it.