Underweight and weight fluctuation

DEAR ASK THE DOCTOR: I am almost 18 years old and I am concerned about my weight. I am about 5'7-8 and my weight fluctuates between 98-103. I am a slim person but this doesn't seem normal to me because I continue to get more than the average person. Is my weight considered healthy and I should not be concerned, or do I consult my doctor?

DEAR EUGENE: Please check back here to see a response from our team of physicians at Ask The Doctor.