S.L.
That sounds like what happened to me when we were trying for #3. The biggest difference is that I wasn't on BC before, and they're only 3 1/2 years between. I can't remember all the details, but it was about a year ago that this all happened. The first month, my period was 2 weeks early. I figured it was implantation bleeding, which is what happened with baby #2. But it was too heavy. Two weeks later it came again! It was crazy and horrible. The next time, I was very excited when the day to test arrived and still no period. But the test was negative. I wondered if I just needed to wait and test a little later, so I decided I'd wait a week and test. Well, I didn't take the test because that morning my period started. I felt so jerked around emotionally! First was a month of nearly constant bleeding, then nothing for 5 weeks?
I'm not one to have irregular periods, either. They just coincided with trying for a baby. Ugh.
I did get pregnant. Later than I wanted, which sometimes I would like to complain about (because he was born on Nov 30 and my mom couldn't stay long to help, and MIL couldn't come at all). But when it comes down to it, he's here and that's all that matters.
Good luck!