The carb issue a real hot topic nowadays. You will certainly lose bodyfat quickly on a low carb, high protein diet, but if you get too extreme with it you also experience that slump and lack of energy. Carbs are not the enemy, they are your most efficient source of energy and fuel. Protein is a terribly inefficient source of fuel for energy, it's best use is for rebuilding tissues. It takes a lot of work by your body to process protein into the form it needs to be in to even be used for energy. Whereas carbs are more easily accessed and stored.
What you want to consider is the glycemic index of the carbs you choose. Things like green veggies have a low index so you can eat a whole bunch of steamed broccoli with some light soy or teriyaki sauce, or a big plate of sauteed green beans, whereas for the same glycemic index you'd only get about a quarter of a potato and a pitifully small serving of pasta. You don't need to eliminate your favorite carbs, just view them as treats more than daily staples. I LOVE pasta, I could eat it 3 times a day forever and never get tired of it. And when I was broke way back when, I did just that! But now it's like my treat when we go out to dinner.
I've also had good results from keeping meals separate in terms of proteins and carbs sometimes. I might have tuna salad with a green salad for lunch, and for dinner have millet with fresh dill and baby carrots and a salad. It's all up to the individual and there are lots of ways to balance your intake. I don't count carbs or track them mercilessly, I just keep in mind that starchy veggies and foods should be smaller portions and green veggies and certain other grains (millet and buckwheat) I can eat till I feel satisfied.
Stopping the soda drinking is a HUGE step and I wish everyone did that. Don't resort to diet colas, either, they're even worse for you.
Carbs tend to make he body retain water, and processing protein flushes and uses a lot of water. That's why you get the quick drop in weight on those hi-pro diets. Bodybuilders have known for years that cutting out carbs before competition gave them more cut because they flushed any excess water. Your body will store any unused calories as fat, so carbs don't "make you fat." Taking in more calories than you expend makes you fat. I think you seem to already know how to balance your food. You sound pretty smart about that. Just keep the portions of starchy foods smaller and less frequent in general. You do NOT have to go the hi-pro way to be lean, your body naturally craves a balance.
I hope that helped at least a little. I wish I could give you a more specific answer, but I don't believe in one answer applying to everybody. There are just too many variables for that.
Take care.