Write down everything, solid or liquid, that you put into your mouth. Literally. There are some liquid options that have a lot of empty calories. It's easy to forget about them but they do add up. Also, are you getting in 8 glasses of water a day? If retention is your problem, 8 glasses might be your solution.

Write down your daily activity and how many minutes you are doing it. Skipping your walk or activity of choice once or twice may be going unnoticed. It's so easy to lose track.
These are just a couple of suggestions just to verify whether or not this is where the problem lies.
If so, you'll have a record and way of tracking in the future.
If not, maybe it's something else and now you'll have a record to show that.
Keep us posted on your findings/successes!