How old are you?
If you are past your prime growing period, you need to do more than simply "eat more" to gain the correct type of weight.
I am 22, 6' tall, and weigh 140lbs.  My BMI is between 19 and 20.
That simply is where my body hovers at.  If I eat 'alot', I simply gain weight in terms of fat around my abs.
Your BMI is 17.8, so I agree you might want to put on a little weight.  Have you habitually ate very little over the past few years?
I did a quick calculation for your body size, and it shows that you need somewhere around 1,650 calories per day.  However, this is a very rough estimation.  This is assuming you are a guy, who is between lightly active, and sedimentary (basically I added on 40% calories to your bodys need).
So if this is close to what you body needs, eating 1830 calories should net you some extra lbs.  But pay attention to how your body stores them.  Are they simply converting to fat in trouble areas? (Abs, for instance.)
If so, you are going to need to do some strength training + extra protein/calories to gain some mass correctly.