To late to start bbt tracking?

I just got a bbt thermometer again tomorrow is cd13 would it be to late to start bbt trading again or should I just wait until next cycle? Recent cycles I haven't ovulated until cd18 also I've been taking opks and I haven't had a high or peak reading yet and I can usually tell when I ovulated so I'm pretty sure I haven't ovulated yet. I just wanted to go ahead and get in the habit of it because I plan on switching to bbt charting instead of using opks. I'm not going to be TTC until I'm cleared from my gyno I'm getting a leep procedure next week. I won't even be able to have sex for 4 to 6 weeks after.