I was on the BCP for 9 years.
When I went off the Pill, I purposely went one cycle without trying to conceive just to see what my "normal" cycle was like. I charted using TCOYF and although my cycle was almost 6 weeks long, it did follow the normal pattern. I charted again the second cycle and was able to determine when I was fertile and we conceived.
I can't recommend TCOYF enough! I have always had long and unpredictable cycles and thought for sure that I would have difficulty conceiving. It turned out that my crazy cycles were in fact completely predictable using basic fertility charting. Both of my kids were conceived pretty quickly.