I have doubles, and remove doubles won't delete them I'm having lot of trouble modeling a room, the general problem is that lines overlap. I tried removing doubles but nothing (all the mesh was selected). There must be something i'm not doing right but i don't know what



Here you can see the lines overlaping
Looks like you don't have duplicate vertexes. Looks like you have an edge on the inner vertexes and another edge from the farthest vertexes. The edges overlap where you circled.
You can try to delete the edges and create them correctly, then recreate the needed faces.