Showed my gp my toenail on suspected fungal nail & she said it did look like it was. took nail clipping for test & result was negative. what else isit?

Micro trauma : If the nail is thickened and the culture was negative it is usually due to trauma to the nail. Could be a big trauma that you would remember but more often it is due to micro trauma over a period of time, like from shoes or activity.

See a dermatologist: Labs may miss toenail fungus. But there are various other possible causes for abnormal toenail. If you want to do something, see a pro: best see a dermatologist.