Visual disturbances

I keep trying the doctor, but the forum is always full, so I hope someone can help me.
I am a woman of 39 with 2 children, in reasonable health. After the birth of my 2nd child at 31, I had my first migraine with a visual aura of a scotoma followed by a scintillating crescent. This happens once or twice a year.
In the last couple of years I have been noticing other visual symptoms, including floaters & other entoptic phenomena, however there are a few things which are now frightening:
I often get a scintillation (both eyes) in the centre of my vision. It almost always happens around the time of my period and sometimes mid-month, at about 9am, and about 20-30 seconds after getting out of my car. I only see it for a second each time I move my eyes or blink, and it fades away. It lasts for between 30 secs and 5 mins, and has also happened once or twice when I have stood up, or gone from very bright light to dim light. When it is there, I close my eyes and I see a dark purplish blotch, no sparkles.
I get a pixellation around my peripheral vision when I cough or sneeze, which goes instantly - is this normal?
I see central flickers/snow when I look at patterns or fussy backgrounds, or stripes; also when i wake up in the night, or early morning, my vision is very flickery for a short time, almost like a mild strobing.
Optometrist exam was normal, except slight astigmatism, but eyes always feel strained. My blood pressure is about 100 or 110 over 70, cholesterol low, weight normal. Blood tests at doc were all normal, although thyroid was suspected since I have been feeling very tired.
I had a head and neck MRI 7 years ago just after the first migraine.
Please help, I am making myself ill with worry, and I know I am constantly looking for more strange visual things which probably makes it worse. I am afraid I am going to have a stroke or something, and the GP dismisses me as a worrier, although I have only been anxious since the visual stuff started.
Many thanks to all in advance, Catherine

[circumspect]

It's likely that your symptoms are a combination of entoptic phenomena, migraine-ophthalmic migraine, floaters, the effect of estrogen variations (menstrual cycle) on migraine and heightened awareness and your understandable anxiety.

In order of preference my recommendations would be: 1. evaluation by a neuro-ophthalmologist, 2. a consultation with a neurologist and an ophthalmologist.

Your previous nornal examinations and tests are reassuring but since the symptoms are changed additional evaluations are indicated.

JCH MD Board certified ophthalmologist.