URINE RETENTION...

Hello all
i have been diagnosed with interstitial cystitis (apart from all the other health issues i have)....which one of the major symptoms is constant urination...a few wks ago i started experiencing the opposite where i had major urine retention...last wk i finally went to the er and was straight away admited with a catheder for the next 5 days...was discharged 7 days later....i am booked in for a cystoscopy in a couple wks and they (the docs) are now telling me that i could have something more sinister like bladder cancer...i am having a pelvic ultrasound next wk and then an mri..my question is has anyone being misdiagnosed only to find out it could be something more serious...should i get a second opinion....a little scared here...
god bless all
sonia