constantly exhausted and other symptoms

[sonne2010]

I am a 33 year old woman. I am often fealing dizzy, weak and completely
without energy. Even the most basic tasks leave me feeling breathless. I am
usually OK the first 3 hours after waking up, although my breathing is most
difficult in the mornings. I have suffered from asthma for 7 years. I have a
very low appetite, and at mealtimes I eat a very small portion and then feel
sick. My friends tell me I look terrible, bags under my eyes and pale. I have
been feeling this way for the last four months. However, every year I have
been having blood tests, and each time they find that my gamma-GT is higher
than at the last blood test. It is currently 71, and the normal among the
population is 40. I sometimes drink up to 2 glasses of wine per evening.
I have been tested for diabetes, thyroid gland problems, lung problems,
abnormal iron level, and all is OK. I do have various (moderate) allergies,
from e.g. pollen, nuts and fruit with pips.

The last 10 years I have suffered from an unquenchable thirst,
and drink up to 4 litres a day and still feel thirsty. I have been to see a
few doctors, and they always tell me that they have no idea what the cause of
these symptoms is. Recently I had a complete-body ultrasound scan and they
found a small cyst in my right kidney. The doctor said I don't have to worry.
But I had a similar cyst im my right leg 12 years ago. Before I knew about
that, I often felt a pain there and went to many doctors about it and got
X-rays. The first 3 doctors said it was nothing to worry about. The fourth
doctor saw it and I had to have a major operation. Now, sometimes I have a
pain in my leg bones, but the doctors say only that it can come from the scar
from the operation. I suffered depression about 10 years ago (first and only
time). Recently one doctor said the above symptoms could be psychological, but
during the depression 10 years ago I did not have these symptoms. Anyway, that
doctor gave me 2 weeks of antidepressants, but I haven't taken them yet.

Can anyone suggest what the possible causes are? What steps should I take now?
Endlessly going to see doctors doesn't seem to be getting me anywhere. I am
very worried that it could be something serious because a good friend recently
died of cancer, so I would at least like to know what it is so I can hopefully
put my mind at rest.