You don't need vitamins, they will only interfere with the fast. You are doing great, hang in there! The first two or three days are often the hardest, this is the tie that your body is adjusting from living off the food you eat to living off it's fat stores. Once the body is free of ingested sugars the body starts breaking down the stored fats for energy, this can start happening anywhere from 18-36 hours after eating. It can then take another day or so for the body to fully change over and start providing full energy and nutrition needs for full body function. It's the changeover period that most have trouble with, it's while we still have cravings to eat for one thing, and another the body is naturally a bit messed up in some ways- it's a huge change to go through.
Feeling lightheaded is probably a good sign that you have already started the changeover and are burning fats for sugars already. So keep going and you will pass that point of not craving foods just to fill your empty stomach. Your body will be providing you with everything you need and it won't desire anything more while there are stores left to burn.