Are you focusing on your nutrition? As a heavier guy it is possible to loose some fat and weight while building muscle. At least this works in my case :D but there are other parameters like the muscle memory that are helping me right now ^^
Have you thought about taking measurements of your waist, legs, chest and so on? Watch them for a few weeks and you will see if something is happening.
Yeah my nutrition is pretty good, I write about my meals for each challenge in the posts I do.
I think atm it's muscle memory, as I am coming off of a 6 month break. My weight dropped a few kilos at first then went back up a few kilos. Not sure what my weight ws the last week as the scales at the gym broke.
I like the idea of taking measurements, will take some this weekend and then I can keep track of it.