Antibiotics Safe During Pregnancy?

Has anyone taken Macrobid during their pregnancy? The doctors said it was safe, but I am just a little paranoid to be taking extra medication. 

I was on Erythromycin for probably the first 2 weeks of my pregnancy. My family doctor told me it was completely safe, but I went off of it anyways. It was rated "B" during pregnancy by the FDA. I'd rather be on the least amount of meds as possible. I'm on Zofran right now because I was having extreme morning sickness and my doctors didn't want me to lose any more weight. Hopefully when I'm out of my first trimester the morning sickness will go away and I can quit the Zofran... hopefully.