Back Pain is not very limited to back area, considering your case is there any provocative factor/activities, what are you reliving factors, some more detail history of pain,it's nature, type, history of weight loss,etc with some special test will let us know whether you back is of back origin or refered /radiating pain. Once coming to conclusion we can then comment on whether forward bending to be avoided & for how long if required. Currently I think (5days session - might be too easy to judge) continue with sessions after detail examination is done (which your physio must have done considering it).
Next Steps
some investigation, test and proper regular therapy sessions (including patient education, postural advices, exercisea etc) will help your way best & answer all ur concerns.