I would say, yes, you do not eat enough. With the right foods (you'll need to do some n=1 on the basic primal diet) and the right exercise (weights, slow moving and a little HIIT), you can probably get yourself to a place where you can eat more food which will supply enough nutrients for the healthiest you that you can be.
In the past the only way I could reach or maintain the weight/size I am now was with extreme dieting combined with extreme exercising. Otherwise I was always gaining incrementally.
I have never been one to measure my calories, but I am at a place where I can eat 3 solid meals a day (or sometimes 2 solid meals and one snack-sized meal) and maintain my weight/size. I've been weight/size-stable for almost 3 years on primal. I would estimate my calories per day are well over 2000. I'm 5'3" tall. The last time I weighed myself I was 137 (but wearing the same clothes and measuring the same at the waist as when I weighed 130 a year ago, thanks to weight lifting).
This is what I look like. Nothing to write home about, but not obese. I'm the woman in the picture.
Female, 5'3", 50, Starting weight: 163lbs. Current weight: 135 (more or less).
I can squat 192.5lbs, press 75lbs and deadlift 210lbs