confused..i need advice and to know i'm not alone

i recently found out im having a baby girl which is super exciting but i really thought it was a boy, this is my first child and i just thought it was a boy. since i found out i just knew (or thought i knew) it was a boy so i have been imagining myself with a boy, now that i found out its a girl it really hit me hard and i honestly feel like such an awful person for it, my boyfriend is super happy because he knew it was a girl but i just was so sure it was a boy, i do love this baby and i feel awful for not being happy..i really do just want a healthy baby but i just don't believe it, i have been talking about the baby/to the baby like the baby was a boy so now knowing the baby is a girl i'm so confused and i know i should of never gotten myself worked up and i should be grateful which i am but i just don't know how to feel. to my family i just act happy and excited but when i'm alone i break down crying, i tried talking to my boyfriend about it but he made me feel bad for it so i just feel alone and i honestly just feel like a shitty person for not being happy or excited like i should be. can someone please tell me im not alone..