I have got braces 2 months back and my face has become so weak and sunken than before. i am already underweight but my face was fine and fuller.help?

Face change n braces: Changes in a face becoming "weak and sunken" after two months of braces is very unlikely although further weight loss due to discomfort or change in diet is possible. And perceptions that by just moving teeth braces can make dramatic changes (good or bad) in facial appearance (on remote deformitiy like cheekbones, chin, neckline, etc) are common. Have your face evaluated by a cosmetic surgeon.

Extractions?: You didn't mention if you had any teeth extracted in conjunction with your braces - in a small % of pts with crowded teeth, it sometimes requires extraction to allow alignment of the rest, and this can have an effect on the face and facial contours. If you didn't have teeth extracted, then it deserves a careful evaluation - ask your orthodontist if you should see your physician.

Lack of Use: I agree it does need further evaluation. Many ortho patients do not chew or bite with as much force during orthodontic treatment. This may be due to soreness or the teeth not fitting together in a comfortable way. This can lead to minor muscle atrophy and not eating as much with some weight loss during treatment. If this is the case, it does get better.

Disscus with doc: You have valid concerns, but it is best you address them with your orthodontist and understand what is going on.

Sunken face: See your orthodontist. He is in the best position to evaluate you concerns, and deal appropriately with them.

Reevaluate: 2 months is too short a time to expect major facial soft tissue drape change. Not knowing your malocclusion or your treatment plan it's impossible to comment. See your MD to rule out systemic problem. If your braces treatment is supervised by a General Dentist, seek consultation with fully qualified Orthodontic Specialist. If already seeing Orthodontist, seek 2nd opinion.