For a week now, I've done a complete change of diet. I've been feeling kinda sick (allergies

) so my meals have been small and far inbeween.
Right now I feel dizzy and sort of generally unwell (worse than before)...I tried eating a few pieces of fruit and I feel a little better but not fully normal.
What should I eat to feel back to normal? I'm not sure what vitamins/nutrients I'm missing, but I do know there's something up.