Sounds to me like you need to put your foot down with where you want this relationship to be... and how its going to go ahead...
Is it still NSA for you? Or do you love this guy now? Either way you need to be clear on the boundaries that YOU are comfortable with... not just by reference to B, what makes you comfortable?
Smile! It makes people wonder what you've been up to
Engaged to my sweetheart, WaterWolf