A CT scan showed several scleretic bone lesions in the sacrum. Could this be normal?

Yes. Many patients have benign areas of sclerosis, often in the sacrum, pelvis and hips. The personal history of the patient, presence or absence of pain, and stability (if old studies exist to compare). If there are concerns, further evaluation with bone scan (maybe with spect if lesions are small) or even pet/ct may be appropriate.
Yes. This is not uncommon. If you have no history of cancer, they are probably benign. If you are worried, a bone scan could be done. If negative, i wouldn't worry about them.