Help! Not excited about baby gender

i had gender scan today ( 20 w 5 days ) and i feel so bad that i am not exited to know its a boy! i love him so much but have always wish for a girl plus my husband has a 10 years old son. i was with him during the scan and he too was not as excited. i just wish i am excited but am here feeling guity that i am not. i feel angry at myself and i wish i am just happy because i love him soo much. any one who had the same feeling? any thought of how to let go of the feeling? thank you