Feeling sad

I was doing really well and excited abou our first iui attempt in a month but my sister in law just told me they were gonna try for baby #4 and I'm devestated. I love my neices and nephews more than anything but I'm terrified that she wll conceive before me and my heart will be broken. I am terrified I will never be pregnant and won't be able to experience the joy of pregnancy and motherhood. I need support!!