Temping is a great way to tell if you ovulate but it won't tell you that you have ovulated until afterwards so it might not be much use to you.

Charting as an overall thing might be better to try as that will help you pick all the possible signs of ovulation before it happens and then the temp rise will just confirm it for you. Once you have ovulated, AF will arrive usually within 10 - 16 days unless you get a BFP. If you haven't had AF since your DS2 was born, then you haven't ovulated yet (unless you have in the last week or two).

Everyone is different and after every baby is different. I have always had AF back once before I have been able to fall pregnant again. My first AF after a baby is usually anovulatory cycle (meaning that I didn't ovulate in that cycle). My cycles are very irregular (especially in the year post birth) so I have to watch for signs of ovulation. I didn't use OPKs because I bought a box of them and didn't use them on a week when I ovulated so they were all negative. I didn't want to keep buying them and found them a bit difficult to interpret anyway so I think it is better to learn signs that your body is ovulating and learn about ovulation as much as you can.

The number of days that you have fertile CM present for is dependent on a number of factors including age, so you might find you only have fertile CM for a couple of days which might make it a bit harder to spot. If you get to know your own body though, you will most likely notice the differences when things start to happen. For me the most viable way of telling when I was about to ovulate was knowing how my cervix feels. You need to check it at the same time everyday, but you will feel differences as things start to happen. You have to be familiar with your body for charting to work though. If you aren't, it can be easy to get confused about what is going on. There is also a website called my beautiful cervix - if you google it, it comes up with a bunch of images of a cervix over a 28 day period. If you can get passed the ick factor, it is really interesting and very informative. I recommend taking a look if you want to do charting.

Temping is still important despite all the other stuff because true ovulation is always marked by a rise in temp just afterwards. You need to be temping if you want to chart so that you can confirm that ovulation happened. It is possible to have all the other signs of ovulation and for your temp not to rise. If your temp doesn't rise, no ovulation happened so you know to keep looking out for it or if AF does arrive that you had an anovulatory cycle. Although it can be frustrating, it is good to know. It also gives you more info that you can give to a FS, if you do end up needing to see one.

Anyway, I hope that is the sort of info that you are after. Good luck and I hope to be reading your PA very soon