Your symptoms seem to be increasing in a sitting posture and with exercise.And also the pain is intermittent.But do you get intermittent fever?and do you have problems with your bowels?And do you get any discharge per vagina?
your symptoms with a degree of fever if any indicates a pelvic inflammatory disease
...well supported by the usg report.Associted bowel disturbance if any also supports the same condition due to pelvic muscular involvement.The presence of scar tissue and nulliparous status also points towards previous endometriosis
However its recommended that you get a detailed gynaec check done with a routine pap smear
and blood checks and then take a call from there...
All the best..Tc