Migraines may be a possibility; however, they only last 15-20 minutes. Have you had any eye surgeries? Do you take any medications? What other medical condition do you have? Do you see any flashing lights? These shapes are there at all times?
It certainly doesn't sound like the typical migraines. Sometimes, the gel in the eye (vitreous) can separate and float in one place (called syneresis). This is a precursor to it breaking up completely and floating around. But your symptoms are concerning. I would advise you to see an ophthalmologist to make sure that your retinas are OK. I also think that you need visual field testing to see if there indeed are blindspots in your peripheral vision. Blindspots in the peripheral vision on the outside of each eye may represent a bitemporal hemianopsia (this can be caused by serious conditions).
Initially, it is called syneresis. It can stay in place (this is prior to it breaking up completely). This is inside of your eye so you can see it with eyes open or closed. Many optical stores have a very small screening visual field testing that is not very precise. When you go see the eye doctors, make sure that you get a full perimetry, not just the screening one.