Maggie,
Who's to say what is "normal" or "right" behavior. You do what is "right" and "normal" for you, as an individual.
I have found that humor has pulled me through many rough and trying periods in my life. Although, there were times when I stopped in the middle of laughing about something, questioning why I should be laughing at such a time or at all. I then answered myself - the pain is too great to sustain each and every minute of the day. I need to find some bright spots in an otherwise somber situation. Those I have lost would have wanted me to find some joy rather than remain in perpetual sorrow.
Keeping a journal is a wonderful idea. The journal becomes a trusted "friend and confidant." Your inner most thoughts and feelings are never judged. You are free to write anything and everything. You can go back anytime you wish and refer to what you've written and examine and better understand your feelings.
You are going through your tremendously difficult and complicated grieving process in the best way possible, Maggie. While I cannot feel the pain you are enduring, please know that my heart goes out to you. Please take care and let us know how you're coming along. And, you have friends here with very big shoulders.