Psa level

My name is Craig.I had robotic surgery almost 4 years ago. Psa level was okay until last April,it read 0.13,then in August 0.19 and my most recent.Jan 5th of this year 0.24.  I had an appointment yesterday, and doc says radiation is required now. Has anyon else been down this path? Should my doctor have been alarmed when the reading was 0.13?  I read an number or 0.0 to 0.2 should warrant a visit. I am worried now that the schdduling person,who made my last appointment says,wow,you havent been in in awhile,somebody dropped the ball...Any suggestions..