Im having bad stomach pains after taking to many ibuprofens and i took pepto bismol (bismuth subsalicylate) but it doesnt seem to work.how long should it take to work?

It may not: Pepto may not be strong enough to counteract damage done by the nsaid. If the pain has worsened suddenly, consider visiting the ED for an evaluation as there is always risk of perforation or other emergent outcome. Also, better medications can be offered to promote healing of the stomach lining and for the pain you were initially treating.