Suggest Remedy For Headaches And Nausea Along With Floaters In Eyes

I see an illusion of fireflies that almost blind my eyes at the most random times. Even after a meal, even when I feel the healthiest and nutritious. After 10-15 minutes of seeing fireflies, I get a major, hardcore headache and nausea. The cycle has always been like that, fireflies, and then headache. I have gone to doctors, but they always say maybe it has something to do with my blood pressure, but when they check it turns out that my blood pressure is still in a normal state. It's been years, it started when I was in high school and now I'm in my 3rd year of uni. Can you please explain what happened?