Yes,thank You. For The Last 6 Months I Have Been

Yes,thank you. For the last 6 months I have been feeling very tired all the time. I am 59 years old and I am a nurse working 12hr shifts in a prison setting. I have always been active with my family and working around my house. As of late it seems that I just have to push myself to do anything. The problem is that I never feel like doing anything because I feel tired. When I do "get about" I feel totally drained and this is so frustrating. What to do?