Yellowish teeth can be due to surface stains from tea/coffee/tobacco, plaque or calculus, or simply the natural underlying colour of the teeth. Since you have already tried several regular toothpastes, changing brands repeatedly may not make a major difference. Whitening toothpastes are mainly useful for surface stains and cannot significantly change the natural colour of the teeth.
Next Steps
* You can try a fluoride-containing whitening toothpaste for a few weeks, used twice daily with a soft-bristled toothbrush.
* If you have tooth sensitivity, choose a whitening toothpaste specifically formulated for sensitive teeth rather than an aggressive whitening product.
* If there is visible yellow/brown deposit, especially near the gums, toothpaste will not remove calculus/tartar—a professional scaling and polishing would be more appropriate.
* If your teeth are naturally yellow rather than stained, dentist-supervised bleaching with hydrogen peroxide/carbamide peroxide will give a more noticeable colour change than toothpaste.
Health Tips
* Brush gently for 2 minutes twice daily and floss/interdental clean once daily.
* Avoid brushing aggressively or using lemon, vinegar, charcoal, baking soda mixtures or other DIY whitening methods, as they can be abrasive/irritating and may damage enamel.
* Reduce frequent tea/coffee and rinse with water afterward.
* A scaling + polishing examination first is a good idea if the yellow colour is mainly around the gumline.