Are you definitely ovulating if you get positive OPK?

[yesnoyesnoyesno]

OPK measures LH doesn't it? Is that a sure sign of ovulation? We are ttc#2 and I'm still BF (morning+evening), will give it up if I need to but have had periods since baby was 6 weeks old. Do I need to? I'm getting positive OPKs.

I believe that OPKs only tell you that your body is trying to OV. It is possible to get a LH surge but then for OV not to actually take place. The only surefire way to tell if you've definitely OVd is to get a cd21 test from your doctor (done 7 days before AF, which for most won't actually be cd21). Charting your BBT is a pretty reliable way too. Good luck!

Ah great thanks I'll have a go at bbt then! I'm on CD3 now , should I start straight away to establish a baseline ?

Yes I'd go for it straight away. That should give you a decent amount of readings to chart before you OV.