Would charting my bbt give me an idea of what's going on?

I'm having some cycle irregularities (I'm 23) and I'm wondering if charting my bbt would give a better idea as to what is going on. I was on the mini-pill for a year (after having baby #1) and then switched to ortho tricyclen lo. That is what I took before I got pregnant with #1 and loved it. Anyway, after 2-3 months of taking that I started to spot during my cycles (right before this happened I did forget to take 3 of the last pills in the cycle) and have all sorts of problems with longer than usual periods and spotting. We switched to Ortho Tri Cyclen and problems got worse so I decided to stop taking BC all together and see if my body could reset on its own. I stopped taking it at the end of May but I have had crazy cycles! I had a 7 week cycle (and of course, I thought I was pregnant), followed by a 24-day cycle and now I'm on week 6 of this new cycle (and am not pregnant--all tests are negative). I am not doing anything to prevent being pregnant, but we aren't having every day either. We had talked and decided we wanted to start trying in August (this month), but obviously it won't really work because I can't pinpoint anything! One thing that remains certain of the latter 2 of my 3 "cycles" since stopping BC is that on day 13 (religiously) I get cramps for 2 days straight. I also had some similar cramping yesterday, which would have been day 13 of this new cycle (except I didn't get my period) Could that be ovulation pain that some women experience? My doctor did an ultrasound to determine the reason for bleeding while I was on BC and things looked fine, but a follow up just in case is scheduled in late Sept. I want to start trying to get pregnant, but I'm wondering if charting bbt would be able to shed any light on this situation. If you think charting is a good idea for me, I'd love recommendations on charting (like what thermometers you liked & where you got them). Thanks~