Dental staining during pregnancy?

I've always had nice and unstained teeth due to genetics, obsessive oral hygiene, and avoidance of coffee/wine and other drinks that stain teeth. But, since my pregnancy I've developed grayish brownish staining on my teeth, especially near the gumline despite being even more obsessive than usual about oral hygiene. The only thing I can think of is the fact that I now have terrible reflux 24/7 that might be messing up my enamel and I had severe morning sickness and frequent vomiting until about 18 weeks. But, the staining is getting worse now and I'm at 25 weeks.

Has anyone else encountered this? What could be causing it? How do you manage it? And does it ever stop or go away? Thank you!