Ummm.. is this an eating disorder?

Im 13 and all I've been thinking about since last july is my weight. Im 5' 3" and weigh 120 llbs. Like im litterally ALWAYS thinking about my weight. I can't get dressed, eat, sleep, walk, or go out with you thinking about my weight. Like, I feeel like im never thin, I will admit to not eating for two days straight then eating again but I barely do that. Anyway, is this an eating disorder and if not what is this called??