Certainly your timing, having sex eight and nine days after your period began, is about the worst timing you could do if you are trying NOT to get pregnant. Don't try that one again. But as the previous poster says, you can't be certain when ovulation will come. Google basal body temperature charting, it might help.
Using that method to avoid pregnancy will end up getting you pregnant. Because, unless you copiously chart your cycle and basal body temp and, test your cervical mucous on a regular basis, then all you'll be doing is guessing at whether you're ovulating or not. Guessing is a very imperfect method that leads to errors. Because there are a variety of different things that can alter your ovulation, some of which you may not be aware of.
If you don't want to get on birth control then at least use condoms. Using condoms is far more effective than guessing your ovulation date.