It is so incredibly normal to feel that way, and I continued to feel it on and off during my pregnancy and even now that I have my two month old daughter. But I also look at her gorgeous face and even if there is a twinge of sadness that I'll never see my own features in her, it practically makes me cry with gratitude for my little miracle. I can't imagine her being any other way other than how she is--absolutely perfect--no matter where those initial few cells came from. I would highly recommend picking up a book called Origins. I read it during my first trimester and it made me feel SO much better about doing DE. It's all about the science of fetal genetics and how much influence you have on how the baby's genes are expressed by the things you do while he or she's in your womb. It was so comforting for me to know that I was having such a huge impact on the person she was going to be--even if that initial little egg came from somewhere else.
Congratulations on your pregancy and I wish you all the best!!