Single lesbian trying to conceive

I've always wanted to have a Baby of my own. To experience the whole pregnancy from beginning to end. Have a child of my own blood. I of course wanted it to happen with my partner who I was with for almost 7yrs. Now a year after we split I find myself making this decision without her. This is all I want, to make a little family of my own. I do have a sperm donor and will be doing at home insemination. But why do I feel sad? This should be such an exciting time for me. I finally have everything in place to start this journey and try to conceive. But I somehow feel sad. Why?