Well, I had irregular period for a few years, due to the fact I was coming off the BC Depo Provera Shot......It realy screwed me up
I took provera to bring on a cycle, then clomid to conceive, but still nada.
I decided enough is enough and didn't take anything anymore.....somehow, my cycles regulated to 27-28 days for 6 months, and the in Feb, I too had an unusual cycle. It came 5 days earier than scheduled, it was light, only when I wiped, I put on a pad, but hardly anything. I told hubby let's do it, to bring it on, but all that happened was the usual spotting and my the toilet bowl would be red after i used it. Sorry TMI

So, it wasn't like a normal flow cycle, but a short spotty one.
I took a test 1 week later, thinking it was implantation bleeding, but it wasn't. Point is.......even though it was a screwed up cycle, you could still ovulate, and become PG. You don't need a regular cycle in order to ovulate, like I thought......I know becasue Iam 10 weeks PG, and due Thanksgiving:) After 3 years TTC