Upset over Baby's Gender

I know babies are a blessing and I feel ungrateful saying all of this....I have a 3.5 year old daughter. I did the Sneak Peek Test and it said I'm having a boy, which the tests have been wrong before. I thought this would help me bond earlier on with my baby. Instead I am so upset that it's a boy, I really wanted my daughter to have a sister. I just don't know how to be a "boy mom" all I know is having my daughter. I'm nervous. My ultrasound is in three weeks I will wait until then to confirm the blood test.