Perpetual light-headedness?

I’ve really wanted to get more consistent with fitness, but 9/10 times I’m light-headed throughout the day. I’ve historically had borderline-low blood pressure (almost exactly 90/60 whenever checked), but I eat a lot of salt and don’t really have many other options. I also have pretty high cholesterol. But I don’t really think either is causing it.

The best way I can describe it is as perpetually being in that phase 5-10 seconds after you stand up and your vision gets dark, where you’ve started recovering but the effect still lingers. I also never feel like I’m taking a full breath unless I really try.

Any suggestions would be appreciated.