Recently, I gained about 10 pounds.

I don't think it's fat, though; I've been eating pretty healthily. However, I've started a new exercise routine (2.25 miles, up a 10 incline, takes 40 mins, and I do this everyday)...could those ten pounds really be all muscle?

Thanks :)

It's unlikely that it's all muscle gain - your exercise is mostly cardio and only slightly muscle strength. If you said you were weight lifting or resistance training that would be different.

That said, muscle tissue does hold more fluid than fat tissue, and it does weigh more. How does your body look? How do your clothes fit? How do you feel?