Iman,
I am not a mental health specialist, nor am I qualified to give a professional opinion, however, I have been struggling with depression and bipolar disorder my entire life. There are times when I didn't think I was gonna make it through. Many times, in fact. But, I pulled through somehow.
I understand how your partner's depression may make you feel. I have a boyfriend that I have been with for 2 1/2 years and he describes feeling very similar to you. He tries to work with me, and sometimes I get better. But then, all at once, I am back where I started. He feels frustrated and unable to help me. He doesn't know what to do for me anymore.
The first thing you should understand is that depression is a disorder with abnormalities in the brain. So, maybe your partner should consider taking medication that will help correct/readjust the chemicals in the brain to help her think more clearly and feel better. Does she take medication? If so, maybe she needs to change her medication and get something better that works for her. If not, have you already discussed medication for this? Do you think its possible to bring this up to her?
Most importantly, know that her depression has nothing to do with you. It is within herself and only she can make herself better. It is not something that can be cured or fixed. Treatments, such as medication, therapy, and changing the external environment can be of good use, but do not make the illness go away. All these things simply make the depression better to deal with, so that when she is feeling her depressive symptoms, she can react more calmly and be better able to manage the symptoms.
Also, what kind of depression does your partner have? Theres major depressive disorder, seasonal affective disorder, dysthimia, depression with psychotic symptoms, etc. How long has her depression been going on?
Answer these for yourself and take some of these questions to a therapist and/or psychiatrist that can help you with finding out her diagnosis and what treatments are proven to work with some patients.
The best thing you can do is just be there for her. Be a really good friend and stay by her side. Let her know how her depression makes you feel. Let her know that you'd like her to get some help so that the two of you can improve your relationship and be more satisfied within it.
Lastly, know that you cannot help her. She has to be open to therapy and treatment. Before that, she has to admit that she is struggling with a disorder of the mind. Let her know that this is not her fault. Let her know that there is nothing wrong with her. Let her know that you care about her and want her to get help. Remind her that she can only start to feel better if she tries to help herself by making an effort.
These are my opinions, being someone who goes through the same thing. However, I strongly recommend your partner discusses these issues with a mental health professional. She is not crazy, and she is not weak. She simply needs help to feel better.
If your partner is not willing to work on these issues and doesn't want help, you cannot force her. Unless she is a danger to herself or someone else, she has to seek help herself from a professional.
I hope this helps and keep in mind that I am not telling you what to do. I am simply offering my advice.
Good luck to you,
Fallabe12
