Light Headed Very Easily, Trouble Focusing, Fatigue, Mental Disturbances, Vision Gets Fuzzy. What Is The Reason?

I get light headed very easily, sometimes to the point of fainting. The light headed spells happen frequently during activities that do not involve sitting or lying down throughout the day. I have trouble focusing/concentrating and reading has become slightly more difficult over the last few years. I also experience mental fatigue throughout the day. While I do not faint often at all, it is common for me to get light headed to the point where I feel as though I might. When this happens, my vision will get fuzzy, sometimes completely going away, and I will feel hot. These spells are random and unpredictable, being triggered by something as simple as stubbing my toe unexpectedly, getting out of bed too fast, or just walking down the street. When I do pass out, it is only for seconds and I wake up hot and with no memory of the fainting itself. This leads me to believe that there have been instances of fainting that I am not aware of simply due to not remembering it. I have been told that I have symptoms of both cerebral hypoxia and an overactive vagus nerve. If this is true, what supplements or treatment options would help me?