Eye dr said optic nerve hazy & sent me 4 mri, as also having nasty headaches, my gp said there was pressure pushing on the disc what could this be?

Papilledema: Papilledema is swelling of the optic nerve due to increased pressure in the fluid of the brain. This candy do two simple excess production of fluid and is more common in women. This is called pseudotumor cerebrae or idiopathic intracranial hypertension. Headaches are common and rarely this can lead to some vision loss. Another unlikely cause is a tumor or growth in the brain. The MRI should help to sort this out.

Many possibilities: But it sounds like you need a consultations with a neurologist at the very least.