I had a ct 5 days ago and 3 x-rays today pelvis/abdomen flank pain all normal. dr wants another ct with and w/o contrast done. is this a cancer risk?

Yes but: The reason the doc wants the xrays may well out weigh the risk of having the test done. I believe the risk is worth the knowledge of what is going on. You may well enough information to prevent further or disease that is present.

Low risk: It does seem to be excessive the risks should be counted through out your lifetime. If you didn't have any other studies requiring X-ray radiation you'd be fine. But this seems really excessive when ultrasound or MRI can be used to get more information. Try suggesting these non ionizing radiation studies

No, not really: Medical use of X-rays causes minimal radiation exposure, so it is considered safe. So you should not worry about Cancer at the present level of CT scanning..