I'm 20 years old....

[Worba]

and I only weigh 116 pounds.

Is that normal or should I be worried?

That's perfectly normal.

[zedxrgal]

It's normal. US average is higher simply because (this is not said offensively) the size of americans has gone up. So if you were to ask a doctor they'd tell you that you should weight 125-130 lbs.
But if you feel fine, look fine are eating healthy then I wouldn't worry about it. As a female's body ages we naturally put on weight anyway as it prepares us for child bearing. I am 5' 7" and weighed 120lbs till I hit about 32 (I'm 34 now) and my weight shot up to 145. But I am not over weight and try to keep my weight in that zone and stay healthy.

But again you're perfectly normal. Allow yourself to put on weight naturally if that's what you choose. Just simply eating more can cause it to be unhealthy weight if it's unhealthy food. But damn those carbs and ice creams are nom.
*races off to eat cookies*

Y'all are fine! Don't worry about it!!!

[Worba]

But if you feel fine, look fine are eating healthy then I wouldn't worry about it.

This. As long as it falls somewhere in the above, numbers don't matter.

[Qinni]

As long as you are menstruating regularly, I wouldn't worry about it.

I am

God those cramp like a mother f- >.<

[Impulse]

Well I seem to be 3 pounds off or so...so I'm going to be eating a bit more. *stopping when I'm full rather then satisfied* I have found myself not eating after breakfast and diner so going to get peanut better and banana sandwiches since that made me blow up like a balloon while I was in school.

As long as you are healthy and taking balanced diet, I don't see why you need to eat more just to add more weight unless you want it for cosmetic reasons. Also it's better to eat little 3-4 times a day rather than skipping meal. But I'm pretty sure everyone knows that already