I feel lonely.
I feel empty.
I feel incomplete.
I was melancholy.
I feel really down.
She looks blue today.
I'm gloomy today.
He was depressed for losing a lot of money.
I'm depressed. I lost my job.
Rainy days get me down.
He was disconsolate after his wife left.
A: Hello, Dora. I haven't seen you for a long time. Where have you been?
B: I didn't go anywhere. I stayed at home.
A: What's up? You look unhappy.
B: Nothing. I just feel very lonely in this city. I miss my family.
A: Oh, I know. Sometimes I have the same feeling with you. But you'd better not be so emotional.
B: Can you stay and accompany me for a while?
A: Sure, no problem. You can call me anytime you're alone from now on.
B: Thank you so much. You're so sweet.