Congratulations! If you've already had a baby, you're in a stable relationship, and youre financially stable and all that, then hopefully your family will be happy and excited for you. I hope you get your wish and have a girl this time. Just remember that your situation is good, and that a lot of girls have it so much worse, and if your family objects, remind them that you're in a good place and really emphasize how happy you are to have another child.
I'm 19 too, first time though so you have that on me lol
I'm sure you'll be fine, you're in a good situation and you've already raised a child, I'll cross my fingers that your family are excited for you :)