I'm not sure of the accuracy of mybodycomp either. I workout a lot (6 days a week weight training and cardio - alternating days) I have a lot of visible muscle. Yes I am short and don't have much of a waist (never have), but I look thin and its telling me I'm at 33% myself. I mean maybe I'm in denial but I'm fairly sure that is not accurate.

Anyhow I highly reccommend a lady named Joyce Vedral for weight training. She is awesome and I think in time you would gain a lot of muscle weight with her. Check out her site JoyceVedral.com.

Good luck.