Lets work on what you have now - as Kevin asked - a phal? Can you post a pic? How long have you had it? How thick is the curtain and how close is your plant to the curtain and window? Phals cannot take too bright light - unless well filtered south may be too strong? What kind of media is your plant in? In the winter months some phals only need to be watered every 2-4 months depending upon media and environment. You might want to check out the AOS culture sheets and see if anything stands out as something you could do to improve your situation and then come back with some more questions -
American Orchid Society - Orchids