I'm so sorry you went through this, but I'm glad you were strong enough to share your hurt with us, as I think quite a few of us can relate strongly to your feelings. My daughter, who lives with me, always forgets (and my birthday too). Kids can be selfish until they need you. Someday they will 'get it'.
Until they do, ALWAYS rely on your canines, they NEVER forget that EVERY day is Mother's day.