My Depression Is Making Me Physically Unhealthy, How Do I Boost My Immune System?

I’m 14 and it’s flu season (yay) and I’ve been pretty down. I have already gotten sick
months ago, and or me, once I get it one a
year I don’t get it again. It’s been that way for me. I felt kinda sick a week ago but didn’t really worry because I eat pretty healthy vegetables and fruits are my main course since I am a Veggie. But my… “mother” <.< doesn't care and buys meat, meat, meat, meat, bagel, meat 3tc.
So I've been eating really unhealthy and very little. I eat lunch and breakfast at school so lunch a small salad and by salad I mean lettuce. Breakfast, a granola bar.
And that's it. How yummy.
Now I'm having coughs and a raspy throat. I have Fatigue and stomach aches.
Is there anything I can do? I ate a apple
Today. I have a couple apples in the fridge. Should I eat those? ? ? ? ? I don't feel like getting sick because I already feel crappy I don't need to be double crappy.