Is it normal that my vision dims out

I don't know if it's blood sugar (not diabetic!!!) but after I sit for a while or get up, my vision gets dark and I see mini kaleidoscopes. I have been known to see mini numbers and auras since I was 3, but now my vision is weird. I'm a health freak and I tend to get anxiety when it happens...But I don't go blind its just it gets dim, I feel a little faint sometimes and I sometimes see mini swirls and things and it only lasts 10-30 seconds. It comes and goes every few months, and sometimes I get migraines with it....