Define really sick. As well as any treatments you had (if you used antibiotics, let it pass, something else). Are you still using the vitamins? If so, post a list of what you are taking.
As one potential hypothesis would be that you majorly messed up your gut biome with either the sickness or the treatment there of. If that is the case, you may want to see some of the links and information in the Resistent Starch thread over int he nutrition board.