I'm begging help me

Carmel • First time mom!
I'm so scared.
Knowing my family don't want me to keep this baby (my mom and step dad said they think I should get an abortion because they think we're young and not ready for this responsibility)
My mom told me she would support me if I decide to keep it but my mom was the only one I knew that would disagree but support me the rest of my family are going to treat this like someone died. Like I died and my life is over.
I know they will all love the baby once it's here but until then I'm struggling so bad.
My fiancé is amazing but my family is really important to me.
I'm hiding it at least until week 13-14 because my bigger sister is getting married and I don't want to be the center of drama but I'm scared I'll be showing by then and then it will all explode in my face.
Please help what can I do?
How do I deal with this and feel whole with my decision?