Not really sure what's going on here...

For the past month or so, my eating has been really weird. I've been very focused on my body and appearance, mainly my stomach and weight in general. I've been trying to eat less thinking that it would make me skinnier, not even sure if it's genuinely working. Anyways, I've been eating average 500-1000 calories and counting them regularly. I think that's alright, but my age is meant to be having 2200 or around that. I regularly think about not eating or drinking at all, and sometimes do but end up eating anyways. That's what confuses me. Sometimes I'm completely fine and will eat loads, and sometimes I feel like I don't deserve this. I've been experiencing extreme mood swings recently. It could just be because I'm a teenager, but it feels more than that. Not sure if that's relevant. I'm not even sure if this is an eating disorder, but wouldn't be surprised if there was something. If anyone knows what's wrong and knows what I can do, please let me know.