Help with sword sharpening?

Well, I have a cavalry sword, and it was sharpened pretty well at the top, but completely dulled at the bottom half, so I decided to sharpen it with a knife sharpener. Before I sharpened the blade, the top half could cut almost completely through cardboard, now the sword just dents the cardboard... Maybe I didn't use the right sharpening tool, or didn't sharpen it right? I held the knife sharpener (oh this sharpener is rectangular) so it was diagonal, and when it was on the blade, I had it going a little diagonal, so it was somewhat on the actual blade, and some of it wasn't (I thought I should do that because if i had put the sharpener horizontally it would dull the blade) This is a manual sharpener.... Thanks in advance.