Starting my diet today

Jaclyn • Realtor. Wifey. Lucky Lady.
Starting my diet today. Any tips or modifications that you could recommend? 
My plan:
Drink at least 6 bottled waters per day 
Egg whites for breakfast
Slimfast shake for lunch
Apples/walnuts and yogurt for lunch
Protein and veggies for dinner.
I also work out an average of 5 days per week. Mostly cardio/elliptical. I burn about 500-800 calories per work out session. 
I've been doing the workout thing for months but still gaining weight! I decided that today will be the day that my eating habits change! (TBH I still ate a lot of fast food and junk). Hopefully now that I'm changing my food choices I will finally lose weight?!