Prenatal vitamins

I've been nauseous for the past two weeks on and off. I get it from the moment I wake up to the middle of my work day(10hr shifts). I only vomited a couple of times. I take my prenatal before I leave to work and I drink water all day. The last four days, I didn't take them. I feel bad that my baby isnt getting what he/she is needs. But if I vomit the vitamin up it's useless either way. My next dr appt is in two weeks so I'm going to ask her about it. Any advice???