I have a 16 year old son, now want to have a girl with my new husband.

I have a 16 year old son, through a previous relationship, and was a very single mom the whole time. I met my husband 3 years ago and he really wants a baby, his first. So, we are trying. I really want a girl this time. #1 I feel crazy for having another kid after 16 years but #2 I love my husband and want a girl. I am now 37, he is 3#. Any tips?