I've gained muscle, but haven't gained any weight?

I've been doing a consistent workout routine everyday of push-ups, crutches, dumbbells, etc. for the past two months because I was pretty scrawny and wanted to gain some muscle. I've gained clear muscle in my arms, legs, and chest (others have noticed too), yet my weight is still around 130 pounds (same as it was before I started working out). What gives?