The EFX is a great machine. I am assuming you are speaking of the Precor EFX ... It used to be my favorite until I found the LifeFitnesss Cross Trainer.

You can do cardio almost everyday, although you should alter the intensity or program each day. Take at least 1 rest day per week. Make some days "hard days" where you go all-out. Follow a "hard day" with an "easy day", where you work at a level that is a bit easier than you know you can handle.

Your progress is GREAT! Over the next 3 weeks, monitor progress and if you hit a "stall", then I would advise increasing time on the machine a few minutes each session, or begin using a random program one or more times per week.

Carb blockers are, in my opinion, a load of junk. Save your money.