I am also an only child. I understand what it's like to have to do it all and not have a sibling to help. When you go through a loss you find out a lot about friends and family. It was so surprising to me after I lost my husband the people that were really there for me and the ones who backed off. Surprisingly, my oldest friend was one that was suddenly someone I didn't know. I began to question myself-- was I not a good friend, was I there for her when she lost her mother, would I do this to her, have I acted like this to others, etc. etc?
It didn't destroy our friendship, I call her once in awhile, I keep in touch, but it will never ever be what it was.
Surprisingly, other people came back into my life and were so supportive and wonderful. So, I am going off on a tangent when I really just wanted to say that the anniversaries are hard. They do get easier - it's true that time helps, and you will get to a place where you will do ok with them. I try to do something in my husband's memory around his birthday and date of death to honor him in some way and just remember that he was here.
Hang in there.