you wrote:

here is my daily diet:

before gym: sometimes nothing, on upper body & legs days I drink a yakult (pro-biotic drink)

Not sure what this drink is and what macronutrients are in it. You pre workout meal is one of your most important meals and you are skipping it or having what sounds like a low cal beverage. You need complex carbs and are probably not getting them with this drink. Sounds like you are running on fumes at the gym, Im surprised you are able to perform the way you do.

after gym: 2 ryvitas with cottage cheese, mixed leaf salad, handful of raw mixed nuts, celery sticks with 1 teaspoon of peanut butter.

Fat should be no existant in your post workout meal and protein should be a quick release (yours is slow) and carbs should be high GI, yours are low.

mid afternoon - a fruit yoghurt or a few pices of fruit or a slice of wholemeal date & walnut bread.

No protein in this meal and little to no fat, not balanced

Dinner - a fresh home cooked dinner, ie: chicken&rice or fish/veg/potatoes etc.

Fairly vague, could be an ok meal or you might be consuming high GI rice and potato

after dinner - fresh fruit or a fruit yoghurt

if i feel hungry later on I will eat more fruit or a slice of date & walnut bread.

Wrong type of meal to eat in the evening, should be lower carb and slow release protein.

I drink loads of water and 1 or 2 nettle teas per day,
sometimes fruit juice

The good thing is your diet isnt structured properly therefor you are not seeing the results you want. IF it was perfect and your werent seeing results then we would have to dig deep. Read my articles on dieting 101 on my site and start applying the rules and you will see changes.

Darrin