Bignomore - good for you on increasing the speed. Believe it or not walking is a great exercise. The key is to make it brisk walking so your heart rate goes up.
The critical aspect to realize is dispite what you see via marketing efforts the reality is that exercise is good for your health but it is diet, not exercise, that will determine your results. You can burn 450 calories at the gym and a single bagle with cream cheese wipes out the effort.
Finally thing to think about. Small movements over time during the day add up to a lot of calories burned. I wore a gowearfit for four months. During that time I realized that sitting at my desk vs making an effort to get up from my desk every so often, taking stairs, parking further way and other small things added up to hundreds of calories a day. Any kind of activity tracker like this, even a cheap pedometer can really be helpful. There is actually a word for this. NEAT. Non-exercise activity thermogenesis.
Goodluck. Sounds like you're on the right track!
"Getting solid information is easier than ever. Getting misinformation is even easier." - Kaplods
Maintaining for two years and I eat whatever I want - just not however much I want. Details here.