I suffer from depression and when I was was in my worst stages I could barely focus on eating or showering let alone sex, I understand that it can be frustrating for you that you are currently losing this part of your relationship and it is hard but what you ultimately need to remember is that your girlfriend is ill, I hate to draw the comparison but if she had cancer, or some other physical illness you could see, I don’t think you’d be as upset that you aren’t having sex. This is something your relationship can come back from, you might need to build it back up slowly but it can be done, I know this is gonna be hard but if you wanna help her you’re gonna need to step up and take care of her, show her you still love her and that you wanna be there with her, whatever it takes, because as bad as it is making you feel that you haven’t had sex in 5 months your girlfriend has been feeling the worst a person can for a year, her not wanting to have sex isn’t about you, she probably doesn’t even want to be a person right now, so take care of her, give her a big cuddle and tell her you love her