21 weeks 4 days

Blessings • (R.N) ----8 yrs of love with my highschool sweet heart, ❤️ baby #1 on the way 11-16
So im measuring 21 weeks and 4 days I just left my doctor appointment and my baby is very active and he weights 15oz is this normal for his size and considering I'm only 5& half months ? Plus I'm weighing 132 I was 110 before becoming pregnant ... What's the likely hood of me having a c section ? I'm trying to have a natural birth