Generally, orchids sold at retail are potted in moss, which does not serve many of us well as a potting medium (although to be fair, some people do great with it and swear by it). Anyway, you may have root rot, and if so, no matter how much you water it, the roots won't be able to take up the water, and the plant will get dehydrated.

My first step would be to unpot it and look at the roots..cut off any that are squishy instead of fat and firm, and see what you have left. Here is a video on repotting one that you may find helpful: http://www.rv-orchidworks.com/orchid...laenopsis.html

Your plant looks just like one I got as a gift last year from a florist. When I repotted it, most roots were not good...but it had a couple, and the air-roots were OK. It recovered. and is in bloom as I speak...so don't give up hope!!!