I kept track of my cycles for about 8 months before we started trying - I didn't do charting or temperatures but I found I had a pretty regular cycle (anywhere from 27-33 days) and my sure-fire sign was the egg-white cervical mucus (EWCM) - but sounds like you haven't notice that sign in yourself. I don't think everyone experiences it, but it was very regular for me once I started paying attention. If you have a regular cycle and notice the EWCM it's a lot easier than charting and temps, but if you don't getting the testers and getting a little more in depth may be necessary.
For me, it usually happened around day 12-15 of my cycle, and from what I read the days you have the EWCM and the following 2-3 days were the best chance of catching ovulation. Sure enough when we tried I had the EWCM on a Thurs and Fri, and we didn't get around to trying until Saturday, Sunday, and Monday. Two weeks later I got the positive test.
ETA: I didn't realize I experienced EWCM until I actually started looking for it - so its possible its happening for you, but you just haven't noticed yet.