Can anyone help me understand?

I just lost my father to COPD. I took care of him at home for 2 months til his final breath on 4/20/2011 @ 5:00am. I was there til the end as his Hospice caregiver. I am the oldest of 4. I have not cried once yet. I have teared up, but not fully let go of my emotions. My father always taught me to be strong. I am now fighting depression, and I feel like I am losing. I had a good relationship with my dad and was always there for him and vica versa, I do feel closer to my mother, she has always been there for me. I can't imagine the pain if I was to loose her. So maybe this is a stage of denial, or just selfishness im not sure. But I hope it passes so I can go on with my life. I'm afraid this is gonna effect my marriage also. Is there anyone with some good strong advise?