It may be that sunlight is too intense for your mood. But it's kind of a vicious circle -- no sunlight, worse mood, which means you avoid sunlight, etc.

Doctors say that we need at least 40 minutes of sunlight to function as biological beings. Maybe you can commit to a short period of time at a time when the sun is not full blast. Early morning or late afternoon. Then once your body gets used to sunlight it will be easier to be in it. Just a thought.