Yes, see a doctor but this sounds like the sort of thing you may need to manage yourself over time. The best three things I have found to help manage a chronically cranky back:
1) crunches each morning. Build slowly, watch technique so you don't stress the back, and a stronger core is a huge benefit. My back problems are now much less often and recovery is much quicker (two days versus two weeks).
2) regular walking. Cycling exclusively can lead to flexibility problems that are only partially addressed by stretching;
3) stretch daily but gently.