How can I make myself eat more?

I’ve been pretty down in the dumps lately and as a result, I’ve been eating once a day. Sometimes it’s not even a meal, it might only be an orange, for instance. Before people tell me how unhealthy it is, I know already.

I am not intentionally starving myself or anything stupid like that, but I get extremely sick to my stomach every time I try to actually eat something substantial.

Is there anything I can do to stop feeling so sick every time I try to eat? I need some ideas, because I’m starting to get so dizzy that I almost pass out every time I stand up. :(