I started getting dizzy spells somewhere around that stage of pregnancy, and yep they freaked me out. Wasn't when I moved or stood up suddenly, wasn't low blood sugar, didn't seem to be blood pressure related either.

I had a trip to hospital - mostly for my own peace of mind - & they pretty much put it down to stress & told me to slow down & that did actually help.

Don't know if that's any help to you, there are a lot of things it could be. Hope you can sort out what's causing it, it isn't nice I know