weight loss and pains

Hello. I am a 20 year old male experiencing weight loss and stomache pains. I have lost 10lbs in 2 months. Even though I have switched to a high calorie diet I cant seem to put the weight back. I'm having pains in my lower and mid stomache, also pains in my lower stomache and blader after urinating. I do have a history of taking advil and other pain medication due to tooth aches. Mostly concerned with weight loss. I'm young, eat well and exercive often. What could be the problem?

[SallyA]

Hello, have you seen a Dr. yet.  Unexplained weight loss and abdominal pain could be due to a simple explanation - particularly considering your age, but could also be something more serious.  Please make an appointment with your GP immediately - don't put this off.  Other things to consider (change in diet, environmental situation, stressors, any type of illness, worms/parasites).  Your Dr. will probably carry out a detailed physical examination and probably order some tests based on what he finds.   Good luck and please get back and let us know  how you go.