Guys and girls, can you explain what may be wrong here?

Hey guys and girls,

Lately I have been working out much more than I did when I first started 2 years ago.
I do cardio exercises and even muscle trainings (especially my chest, arms, back and abs).
Once I even walked and ran on the treadmill, burning 1000 calories!

But there's one thing that kinda bothers me.
I am not losing any pounds (or kilograms as we use in The Netherlands, where I live).
My length is 6' 6" (195 centimeters) and my weight is approximately 214 pounds (97 kilograms).
I keep having that weight though I work out a lot, besides that I also eat a lot of food with a lot of protein lately.
But I have a very slim posture.

Is this maybe because I am building muscles?

Let me know!
Guys and girls, can you explain what may be wrong here?
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