Are there natural ways to enhance your breasts?

No. There really are no "natural" ways to enhance breasts. There is a suction device called brava, which is a non-surgical option.
Yes. If you can tolerate a major degree of inconvenience the breasts can be expanded with the brava (a glorified pair of suction cups) for one month before and after fat grafting surgery and you can enhance about one cup size per surgery.
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.
Yes. Use of your own fat in the form of a graft is becoming a well accepted alternative to artificial implants. It is important to find a very experienced surgeon in this area.