I used to be very healthy and weighed 125 lbs/ 5ft 8, but recently I have lost lots of weight. I now weigh 111 lbs. I don't understand why I lost so much weight, I have not changed my diet. I still work out and go for daily walks. I also used to have lots of energy but now always feel tired and fatigued. Ive also experienced headaches and have started waking up with stomach aches. I visited my doctor and she said I was healthy. Im very confused about this and would like your opinion.

So your doctor did a full set of blood tests, to check varioius levels of chemicals in the body,

so your doctor did a full set of blood tests, to check varioius levels of chemicals in the body,

Well, no nothing that extensive.