Anything which involves a sudden loss of vision within the eye(s) need to be looked at urgently. Forget dealing with your local GP, this is something that need to be seen by a specialist eye consultant, so please make your way or get someone to take you to the nearest Emergence Hospital which has an Eye Clinic Department ASAP.
It might transpire that your problem isn't so serious to warrant the Emergency, but none of us here as well as yourself won't know that until a specialist consultant in Eye disorders can examine you more closely.
The White patches that are blanking out parts of your vision are common where the blood supply is cut off from parts of the Retina and this again is something that needs urgent attention..
Sorry if this reply tends to panic and worry you, but in such instances time is often a critical factor in achieving a good outcome.
What you experience happened to me many years ago and at the time I left things for a week hoping that things would get better, but sadly for me they didn't and I greatly regret not going straight to my local A&E much earlier.