I am 26, 5`7 and weigh 139 pounds, and waist size 32, am I underweight ?

I work for the Government, but work with the military, on a military base. A couple of weeks ago, we had a Employee Heath Day.(whatever) Anyway, my sup, made me go, they took my weight, and waist size etc. I was told for my age, height, waist size, and weight, i was too small(for a male). which i was told by my doctor, i was fine. is this true? or was it because, i was tested by people in the military?(the ones who did tested me, some of them thought i was in the military, and they were going to try to work with me to gain some muscle etc) i do know that eventhough i am thin, that i am out of shape, but i did not think that it was that bad, the way they are making it out to be.