As an adult, I've always had problems taking multivitamins... actually all vitamins except for children's and Vitamin C gave me stomach problems. Then a couple of years ago I was catching a cold and a friend of mine introduced me to Emergen-C...
It didn't bother my stomach, and even though it calms to give a boost of energy - it doesn't make me feel jumping or shaky(I tend to be sensitive to BOOSTS). But when I'm starting to feel sick I take two in a day and I start to feel better quicker. I use this as a multivitamin now... and I love it.
I've recommended this stuff to a couple of friends who have sense starting using it. This is not a paid endorsement, just me telling a friend (you) about something I like and you might like to try also.
Check out their website: http://www.emergenc.com you can send away for free samples of Emergen-C before you buy.