Why do I keep forgetting to eat?

So for the past few days I've been forgetting to eat (I know it's not healthy). Truth is I don't even do that much (since it's summer) I read, watch my shows, hang out with friends and that's about it. The only time I eat is when my stomach growls, and pretty much reminds me that I haven't eaten anything all day, so I eat something like a sandwich and that's it. I mean, it's like a nuisance to eat. I will eat when my stomach growls or when theirs food in front of me, but I won't enjoy it. I've never had any eating disorders and I'm 13, female, 4'11'', and 106 pounds (if that matters).