When you take them, are you taking them after eating a meal? They can make you feel sick if you're trying to take them on an empty stomach.
If they still make you feel sick, I'm not really sure what to suggest. Maybe there is too much of something in them. If you can, maybe ask a doctor, or wait till you're pregnant when you'll see a doctor.
The good news is if you can't take them pre-pregnancy, it's not like your body won't be healthy enough. It's just good to supplement. From what I understand you take them in pregnancy so you can be supplemented the vitamins your baby takes from you - the baby will get all she/he needs. If you have a good diet, everything should be fine (shoot I had not the best diet and everything was still fine with baby). I'd focus on just eating healthy more than the vitamins.
