For many of my circuits shortly before going solo my instructor used to look at the yachts out the window with his arms crossed and feet tucked back off the pedals.
He didn't give me advise or critisise my flying. He only said "Good" after each landing. The feeling I had at the start of this process was "I must be doing something right - he didn't say anything" and when my confidence started to build I got to the point of "What is the point in having the instructor in the AC ... I'm sure I can this myself" only when he got out of the plane did it occur to me that although I knew I could land the plane he was my get of of jail card.
He said the way he gauges if somebody is ready to go solo is asking himself "Would I be confident enough in his landings to have my wife fly with him?" ... my reaction was "You can't like your wife much"
Belive in yourself - your instructor wouldn't send you solo if you didn't have the ability. Do a few more 'solo' circuits with a 15st ballest/instuctor in the other seat.
Good luck.