Hi Beatriz and welcome to the forum. On the assumption that you are also new to the site, this FAq should help you find your way around.
Welcome to Benefits and Work I'm afraid that DWP and ATOS are both very behind with ESA claims, it is not unusual to hear of people waiting many months for a decision.
The only thing that I can suggest is to get your MP involved, Even if this does not speed up the process, at least your MP would be aware of the way this is affecting people.
Contacting your MP