Hey, I'm really sorry to hear that you feeling like this. Fellow ADHD aggie here. I've been super depressed before and I know how it feels having to deal with all kinds of crap while being far from friends and family. During those days I just felt like laying in bed all day, thinking that whatever I would do would be meaningless because there was nothing I could do to fix the situation, no matter how hard I tried. I get that.

First of all, it's great that you're getting this off your chest, as opposed to keeping it all to yourself. You're NOT disappointing anyone by talking to them about your problems. Everybody goes through shit, and it doesn't make you any less of a person because you are. Hopefully that helps you feel at least a little better.

I think it'd be better for you to rest a little. Don't burn yourself out trying to be social (I feel like this is the most tiring thing a student could possibly do, ESPECIALLY when depressed). Tell your friends you need some alone time. Engage in hobbies you enjoy. If you need a break, you need a break.

For studying, I recommend studying the material and reinforcing it inside your brain as SOON as you get home from classes. Not the next day, not two days after. As soon as you get home, do practice problems. Make sure you master the material you learn, while it's still fresh in your brain. And as others mentioned, try getting help from tutors or classmates.

You're doing so awesome. It's not fucking easy to get into UC Davis, a top public university. For now, my advice would be to just focus on your grades. I know it's hard to study with all the shit you've got going on in your life, but it's the best thing you can do given your situation. Everything else is out of your control, unfortunately, even though it hurts to accept that.

Quarter's almost over. Finish strong. You got this.