I'm sorry, Moon. Whatever you're going through, I know it must hurt.
My best advice is to simply be with it, to feel it, then express it when ready.
With the two major bereavements I experienced last year, I found great help writing about it here. The outpouring of support was a remarkable comfort.
And for help in person, I can't recommend recommend highly enough the resources and small groups found at www.griefshare.org.
Loss can at times seem unbearable. It is hard to handle. Now a lot of times when one can't seem to get out from and unbearable sadness from grief that effects their lives is because there are other issues under the surface. You could be having difficulty resolving so many issues surrounding this it can be hard to pinpoint.
It could be a result of feeling responsible or blaming yourself about his passing. Now it may be hard to not feel responsibility but that is one thing you should never do because it is not your fault. Focus on the positive of what you DID do to help him, how you DID influence his life in a positive way.
Also the issue could simply be you need to learn to truly love yourself. A lot of times without realizing it we put so much of our worth on the person we are in a relationship with and your whole world becomes about that other person, you feel you are not whole without them or that they complete you. While on the surface this seems romantic and wonderful but it really is a reflection of lack of love and confidence within the individual. When you can fully embrace who you are, love yourself and feel like a whole all by yourself love of others transforms. It becomes healthier and you can give more of you in a relationship because it is a confident, strong, you who loves yourself and is secure in herself and in this world. You begin to realize that people in your life don't and shouldn't complete you but they compliment you and enhance you. It is a difference that you notice only when you get there something hard to explain unless experienced. Often without realizing it the love we experience is a dependent love, you depend on that person for your happiness you see that person as your happiness. But when you love yourself first and foremost love becomes different, it is subtle and hard to explain but it is that person isn't your happiness but you feel happy when around them. It is really hard to put into words here but it is a difference you recognize when you reach that place.
Therefore the real issue might be you need to truly learn to love yourself which can honestly be the hardest thing you will ever do. It can also be a mix of several issues, not loving yourself, feeling guilty or like there are things left unsaid or undone. All you can do is truly search your soul and see what it is that might be holding you back.
Of course feel all your emotions you are allowed to feel them. Sit alone and just scream if you want, feel every emotion, fear, anger, sadness, etc. Of course I am NOT saying oh just get over it what I am saying is work through this get to a healthy place with it. But grief can be so overbearing in a person's life that it is then not healthy. The grief may always be with you and that is ok as long as you are able to turn that grief into healthy grief. When you grieve in a healthy way the grief transforms from sorrow to almost appreciation, respect and empowerment.