Hi, Susan! I agree with the previous poster that it's probably time for you to bring in interval workouts, and Cathe's Interval Max is the best! Intense Moves by Reebok / Gin Miller is good as well, and the Cross-Train Express series ("CTX") has a Step & Intervals workout as well.
I also agree that it's time for you to start upping your weightloads and intensifying your weightlifting program. Pure Strength Series OR the Slow and Heavy Series, in addition to CTX and I-Max, would be a good bunch o' workouts to invest in.
Hope this helps -
Annette Q. Aquajock