Before i had my son 3 yrs ago i could literally time my period, 28 days on the dot.now i am trying to conceive and it is all over the place. why?

Hormones: So something has changed. Either the brain is not communicating well with the ovaries or there is a problem with the ovaries themselves. I would recommend an evaluation sooner rather than later since this is a change for you. That is more worrisome than if this happened your whole life. Most likely there is a simple reason but better to be sure.