Well, I have a few ideas.
1) Try taking the vitamin just before going to bed (but also with some food). That is a suggestion for many pregnant ladies dealing with constant sickness, so it may work for you too.
2) Try a chewable vitamin (they actually make them for adults too- even prenatal ones!).
3) I started taking my husband's multi for a while but they made me feel sick (a little nauseous, but mostly gave me a pain in the middle of my gut), I switched to a prenatal and that solved the problem. I think DH's vitamin (I think was Centrum brand) was just too strong for me- like maybe it was meant more for a man's body, not a woman's. So maybe all you need to do is switch to a women's multi or a prenatal (if the one you're taking now is not)???
If all else fails, the children's vitamins are better than nothing at all! :)