Hey, Barb, your riding schedule is really commendable. Don't worry too much about speed right now---the point is to ride and enjoy it. (I have been riding casually for a coupla summers, but now am training to do a 50-mile ride.) One thing I've tried lately is a version of interval training---I speed up to 16-20 mph (whatever I can handle) for as long as I can do it, then knock back to my usual 13-15. I don't have any idea if it's working, but I thought it would gradually help me increase my speed.