Question Re Prostate Cancer. Prostate Removed Surgically 6 Weeks Ago,

Question re Prostate cancer. Prostate removed surgically 6 weeks ago, using robotic surgery. Successful without complications. Follow up PSA came back at below .28 using a LIFELAB test. Doctor recommends follow up radiation on entire prostate bed, for 6 weeks. Worry is complication of impotence and /or rectal bleeding. Should I be worried? Do I need 6 weeks of radiation or should I have 3 weeks with a PSA test to determine if 6 weeks is necessary? Does the risk of complication go up with duration of radiation?