Yes -- I took insulin throughout both of my pregnancies. Insulin is a Category C pharmaceutical. Without it, both my baby and I would have died. I also took an antibiotic during one of my pregnancies.
I don't think the previous statement about "Category C means suspected of hurting the baby" is accurate at all! It has more to do with the fact that there are no scientific research studies to definitively document the impact on the fetus. And, really, what pregnant woman would sign-up to participate in a drug study while pregnant?! Basically, these drugs will always remain "Category C," as no one will experiment on pregnant woman.
There are many, many drugs in this category that are safely prescribed by OBs who have the expertise to determine if the need and impact to your body (and, potentially to your baby) outweighs the potential risk. The first thing I would do is ask your OB what will happen to you and your baby if you don't take it. And ask what will happen to you and your baby if you do take it. Then make your decision. But I'm willing to bet that you have a very acute need for whatever is prescribed. The last thing your OB wants is a lawsuit from you. She is looking out for the health of you and your baby.