MarcyL, awesome that you are an OB (I am a retired high risk L&D RN).

Honestly, you may want to rethink the diet soda. The Heller's were not fans of artificial sweeteners, and I did find I seem to react to the taste of sweet as if eating a real sugar of some sort. I can get cravings from fruit tea (sheesh!).

I learned to love unsweetened flavored seltzer - love the bubbles, and enjoy flavors like lemon-lime, blackberry citrus without any cravings as a result. I even find the coconut seltzer to just be a treat

With time, you will find how to adjust your program to work best for you. In my past success, what worked for me was calp, not eating after 5 pm, and a daily calorie limit of about 1500 - 1750 calories. This was how I lost 216 pounds over 4 years.