I'm a little shorter than you and I'm 135-ish. My friends think I'm a stick.

You're active. You need to eat to fuel those workouts. Redrhodie has good advice. I'm not nearly as active as you (though does refusing to turn the heat up too much count?) and while I haven't tallied it up, I'm probably eating 2000 calories a day. I would be very unhappy on 1600, as would everyone around me.