I'm not perfect but my diet has been reasonable lately..
Today for breakfast I had protein porridge made with almond milk and semi skimmed, honey and blueberries. Plus 2 coffees.
Lunch was a protein bagel with a light covering of philadelphia light, ham, cheese, cucumber and a little mayonnaise.
Dinner was 2 slices of small wholemeal loaf with a small amount of butter (real stuff) light mayonnaise, avacado and 2 boiled eggs.
I did have a bit of cake, a biscuit and I'm drinking wine but I've done a 4 mile school run on foot, spent the best part of 6 hours on my feet at work and been for a run. I am at my calorie limit of 1600 for today but I'm very short and only a little bit overweight so I get less calories than someone taller/heavier.
I'm not the most accurate of loggers but I leave some spare daily to account for that bit of cheese or the cake.
If I were you I would just start slowly, if you want to log calories go onto a website which gives you a suggestion based on your activity levels (Google TDEE calculators) use myfitnesspal to log your foods and try that.
Or just aim for more fruit and vegetables, less processed stuff, more variety. Omelettes are great for breakfast if you have time, use whole eggs or egg whites and fill with things like tomato, peppers, onions, ham, cheese, spinach. I eat so much spinach because it's so easy to chuck into something like pasta or an omelette. I have a carton of egg whites from the supermarket that I mix with a whole egg, I'm not going to lie, a fully loaded proper egg omelette with a shed load of cheese is much nicer but it's not great long term.
You can do this, it's hard, it's horrible and you will want to quit. Even if you fall off and have a load of cake one day it's fine, you need to give yourself the things you love sometimes or you will end up being miserable and going back to eating how you were.