When you add an acid to water, pOH changes because you have a lot of H ions which are shifting the equilibrium to the right. So why is is that when you add ethanoic acid for example you produce H and ethanoate and ethanoate may react with water to reform the acid and OH- ions? Wouldn't that change the pH once more?

What I mean is if you for example add 2moles of ethanoic acid and you increase the concentration of H ions to x. So the ethanoate decreases once more that pH because it reacts with water to form some OH- ions?

From one point of view, you can say that first, there are x moles of H formed. Then, there will be 0.01x (rough number) moles of H converted back to H2O, then 0.00001x moles of H being formed again, and so on. So eventually, you get a constant amount of H being formed and a constant amount of H becoming H2O, so that overall the amount of H remains constant. This point is, however, a point where there are more H ions than OH ions.