Question
Help-- I am killing my first orchid! the leaves are lightening and whithering. I haven't moved it, or changed its watering habits, it was doing great until recently.

Answer
Beckie, it is likely that your orchid has roots rot.  You need to obtain some special orchid potting mix. Soak it while unpotting you plant.  Rinse off the roots before repotting and remove any roots that have collapsed.  Firm roots are healthy and turn green when wet. The collapsed roots are the reason for withering leaves.  Repot the plant into  aplastic pot with lots of drainage holes and set where the fresh potting mix can drain out of the pot.  Do not water for at least a week.  It may take a few weeks to begin to genertae new roots and leaves.  Only water in the morning and only when the potting mix is nearly dry.  They prefer an east window .