When you gain weight, what is the first change you notice?

doesn't building muscle make you heavier...not fatter

Muscle is considerably denser than fat, it's pretty common to gain a bit of weight as you gain muscle mass. If you keep up your training regimen then once your muscle mass stabilizes you should continue losing body fat and your weight should stabilize then begin dropping.

muscle weighs more than fat

The question is whether or not you seem to be gaining fat, as ZeroG mentioned, muscle weighs more than fat, so you wouldn't want to look at numbers but the slimming or widening of your face, belly, legs, and arms, and pinch something to see if it's fat (soft, squishes easy) or muscle (harder, can't squish much)

Probably nothing,as long as you feel good that's all that matters.

Might be muscle mass? Not much bad about that, really.

What kinda excersize

Nothing. Muscle weighs more than fat

You are building muscle

Youre doing good. Keep that shit up