Tested for yeast infection, std, and others, all negative, had irritation and redness around vaginal opening. what could it be?

See answer: Consider possibility of vulvar dermatitis that can be caused by anything that comes into contact with and irritates the sensitive skin around the entrance to the vagina such as the detergents used to wash underwear, panty liners, fabric softeners, perfumed toilet papers and pads, soaps, perfumes, bubble baths, shower gels, vaginal deodorants, lubricants and spermicides, and latex in some condoms.

Still maybe yeast: Yeast may still be the best bet. Yeast is the most common vaginal "Irritation and redness" and can be difficult to confirm with standard testing. Talk to your doctor about whether it would be worth trying a treatment for yeast to see if it helps. If it doesn't, ask for referral to a gyn who specializes in infections or vaginal diseases. No STD is a likely cause of such symptoms. Good luck!