As far as your specific imbalance, it sounds like the muscles on your inner
left side side have atrophied (shrunk). The reason your muscles have
atrophied may be muscle imbalances.
If the muscles on the one side are excessively strong they may perform the
majority of the muscular actions which will cause one side or part of your
muscles to be neglected. Move it or lose it. If the muscles on the
inside of your lower body have not been contracting they will atrophy.
The bullworker may have caused the muscle imbalances if you worked
one side more intensely than the other without knowing. It is unlikely
that this caused your posture problem.
It is more likely that something chronic such as incorrect prolonged seated
postures which caused your posture problems. Think long and hard and
examine some of the positions you have either sat in for long periods of time,
or slept in and you will most likely find the origin of your muscle imbalances.
In order to correct your muscle imbalances you most likely need to find which
muscles are tight, weak and lengthened. A personal trainer can easily see
certain muscle imbalances. Personal trainers look at the muscles in
relationship to joints.
A chiropractor would probably suggest your spine or hip is out of alignment.
This is another opinion which would explain your lack of muscular action leading
to atrophied muscles.
Once you find out the origin of your muscle imbalances you can stretch the
tight, overactive side which will allow the atrophied side to contract properly
during exercises for both sides. Stretching the overactive side is more
effective than trying to strengthen the smaller, weaker, lengthened side.