I (18 male) am struggling to support my girlfriend (18 female) and really need some guidance.

Here's an alternate version of your text: "A bit of background: My girlfriend (18f) and I (18m) have been together for about a year and a half. Initially, everything was great, but after we reached the one-year mark, things started to decline. I understand that getting comfortable in a relationship can mean relying on each other, and while I appreciate her doing this, I also want to support her in any way I can. Recently, however, whenever I try to help her feel better—whether through a phone call when I can’t be there in person or by doing something nice for her—she often responds by saying I don’t understand what she’s going through and that I never will because I’ve always had what I want. While it’s true that I've been fortunate, I’ve worked hard to achieve what I have and made significant changes in my life to get here. This cycle repeats every time I try to help, and it leaves me feeling lost since she doesn’t seem to listen. About her: She’s quite introverted and has only a small circle of friends. She's trying to pursue a music career, but it hasn’t been going well. I’ve suggested she consider different coaching options, but she’s resistant to that. She has struggled with feelings of not fitting in for a long time, which I find hard to believe because she’s genuinely fun to be around. She’s been dealing with significant depression for a while now, even before we started dating. I truly love her and want to help, but I feel powerless to do so. I’ve tried everything I can think of, even seeking advice from friends, but nothing seems to work. I’m reaching out for guidance because this situation is taking a serious toll on my mental health, and I’m feeling overwhelmed."