Can masturbation change how vulva looks? Make lips and clit bigger and darker? I noticed that since I started. Also can a doctor tell if I masturbate?

Here are some ... Non-traumatic masturbation would change the size and color of external genital organs / structure. Instead, the process of maturation darkens its color due to heightened estrogen effect and enlarges its appearance which naturally stops after marking into adulthood. However, pregnancy will further darken its color and childbirth may slightly alter it appearance. More? Seek pro-counseling timely ...
Probably not. The tissues of the genitals are quite resilient and flexible. The appearance of any tissue on the body can be affected by use or abuse, but all tissues of the body are able to maintain their normal appearance despite most activities including intercourse and masturbation. Of course with extreme use or abuse any tissue can be changed from it's normal appearance.