I don't think weight matters at all. I know some people who are 5,8" 165 pounds who where a size 14 and there's people like me who is 5,8" 160 pounds and I wears a size 9. It's all about how much muscle a person has. I would go by a tape measure...or get your body index measured. Women are so hung up on weight. Muscle weighs more than fat!
I wouldn't say that your fat. But I wouldn't say you were stick skinny. Your in the healthy weight zone but it also wouldnt hurt to lose a few pounds.