Having been in this boat before I would bet it's your diet letting you down. You may now be at the point where you need to be more precise than just cutting down portion sizes and generally eating better.

Record everything that you eat and you will probably see where you can improve. Cutting the Coke out altogether will make a difference without you doing anything else. For example, my DH can't say no to cheese. When he did stop eating it he lost 6kgs in a month without doing anything else. (he eats a lot of cheese lol).

You are doing so well. I lost 12kgs (over 17 weeks) a few years back and I found the hardest part was putting in the consistent effort. It was easy to eat well and exercise for one day, even one week...but to keep going and keep going even when I didn't feel like I was getting anywhere definitely took a lot more discipline than I thought it would.

Just keep swimming, just keep swimming (Dory from Finding Nemo )