Oh girl........
The thank you notes were the very, hardest when H died. I just could not bring myself to do them, for weeks. Yet, a lot of people gave money to H.'s foundation, and I could not just let them think we had ignored it. Finally, 2 months after she passed, I psyched myself up, and just did a marathon blitz, trying to be as brain numb as possible, and I just copied the same note over and over.
I know how hard it is. Writing a note was yet another sign that her death was real. For you, I am sure it is the same. Give yourself some time, and know you have a pretty large grace period when it comes to things like this.
Hugs.