In this paper is developed carefully an original theory of dark matter, whose main hypothesis is that DM is generated by the own gravitational field. In this work is introduced the best version of the theory physical and mathematically, previously published since 2014. The hypothesis of DM by gravitation has two main consequences: the first one is that the law of DM generation has to be the same, in the halo region, for all the galaxies and the second one is that the haloes are unlimited so the total DM goes up without limit. Both properties are crucial for the success of this theory. Apparently the hypothesis of unlimited haloes would seem impossible but further cosmological studies may demonstrate that dark energy may counter balance the growing of DM. This paper is similar to one previous paper published in 2019, although there is an important newness, which is the new rotation curve of Milky Way published by Sofue,Y. in 2020. Results got with this new data in Milky Way back strongly the rightness of DM by gravitation theory. This work begins studying the Rotation curves data come from Sofue,Y.2015 for M31 galaxy and from Sofue 2020 for Milky Way. Thanks these remarkable rotation curves, both regression curves at halo region are fitted with power regression functions whose exponents are the same for both galaxies. By the fitted function is possible to calculate a dark matter density function depending on radius which is transformed into a DM density depending on gravitational field. This change is the core of the theory because at such moment it is possible to study the formula of dark matter density by the Buckingham theorem in order to change the statistical calculus by physical formulas which depend on the Universal constants G, h and c. From now on the statistical theory becomes a perfect physical theory that despite it is based on the Newtonian framework allows to get new formulas such as DM density and total DM mass. In chapters 10 ,11 and 12 are calculated masses for M31, Milky Way and M33 with excellent results. But it is in the chapter 13 where are calculated the most brilliant results got in this work. (Truncated by viXra Admin to < 400 words)