Can interstitial cystitis cause sharp shooting vaginal and rectal pain in addition to cramping w/ full bladder? a urologist i knows says "nope". ic doesn't do that.

Yes: Ic can give you pelvic pain and ic is also associated with more chance of having endometriosis, which can often cause pain in the pelvic or rectal areas. See a gun who has experience with ic and endometriosis.

Consider workup: While it is possible that ic can cause quite severe pelvic floor pain, you should be seen by a urologist who is familiar with ic. Make sure there is not something else going on to cause your pain, such as endometriosis, infection, abscess, mass.

PFD: Pelvic floor dysfunction is commonly associated with ic. Treating one requires treating both. For pfd treating the ic ( if that's really going on- could be only pfd ) is important but you will need treatment for pfd as well(pelvic floor therapy, aerobic exercise, injections) ruling out endometriosis is a good idea too. A gyn or urogyn who deal w pain is a good bet.