Natural? What do you mean by natural? Non-surgical? Mechanical? Weight gain? Bio-identical hormones? Garments? Vacuum devices? Duct tape? "chicken-cutlets"? Pads? Exercises? Few of these provide sustained desirable results. Hormones may stimulate early breast cancers. Expanders may increase breast by vacuum. Fat injections are another natural method. See http://www.Fattransferbreastaug.Com.
Not really. Although there have been some claims of herbal combinations that may increase the size of your breasts "naturally." the results are inconsistent and not very dramatic. Your best bet will be to consult with a very experienced plastic surgeon if you are not pleased with the current condition of your breasts. I or whomever you consult with should give you all the time you need to go over all options.