More muscle defintion than in my teens?

I'm 21 and my body seems to have changed from when I was a teenager, despite not really excersizing- its weird, I weigh the same but I always used to have a chubby face in my late teens and no muscle definition, whereas now I do, so I just look slimmer even though I'm not- anyone else had a change lke this- also I am female BTW, not male.