I chart my temp and CM, and I use OPKs. OPKs might be a good route for you, since your cycles have a history of being irregular. You can buy Wondfos really cheap from Amazon... like 50 for under $10.
I've always had really regular 30-day cycles, so I just figured we could BD a bunch toward the middle of the cycle, and I'd be good to go. When it didn't happen the first month, I decided I'd chart just for the heck of it, and I discovered a luteal phase defect. I'm pretty sure that short LP is what led to my loss last cycle. So I've been taking B6 to correct it, and it's helped a lot. I never would have known, though, if I hadn't charted.
I use FertilityFriend.com. You can click on my ticker below, and it will take you to my chart. You can sign up for free.
Whenever you get started charting (and I'm hoping you don't even have to!), feel free to ask specific questions. I'm a nerd and love admiring mine and other women's charts.