I'm new mom I have question please help

My doc told me few months ago that my vitamin D is very low! She told me to buy over the counter The vitamin D so I did and I'm taking it every morning with my prenatal I'm 29 weeks 4 days when I went in last Friday they did the blood work and they told me it's still low but to keep taking it. How can this affect my baby? So worried please if someone had something similar what was the outcome was everything okay with u and ur baby???