First of all I would strongly recommend you go to your GP and ask for blood test so they can check things like your iron, B12 etc levels
Then what do you tend to eat/drink in an average day? Do you have a lot of caffeine? Do you drink plenty of water? And how is your sleep?
In terms of food/meals you want to go for a good balance of slow release carbs (brown rice, wholemeal bread, wholemeal pasta, quinoa, oats etc) with protein (fish, meat, eggs, cheese, beans/lentils, tofu etc) and then veg
So an example could be:
Porridge made with milk and some nuts/seeds with fruit
Peanut butter on toast
Scrambled eggs on toast
For lunch you might have
a wholemeal wrap/pitta with tuna/chicken salad and a piece of fruit / some crudites
beans on toast
hummus with pitta bread and veg sticks
oatcakes with cheese
a bean based soup with a roll
Then for dinner things like
fajitas
frittata
stir fry
pasta with some sort of sauce and protein (e.g. prawns or chicken)
Then for snacks fruit, nuts, malt loaf, yoghurt....
Please do go to your doctor though