Can you use OPK's while B/F or does B/F make the results unreliable?

If you can use OPK's while breastfeeding which would you recommend?

My cycles are irregular as a result of the B/F so I was think of using OPK's for a whole cycle to see if I'm ovulating. Do you think this would work? Is there any other way to tell if I'm ovulating?


On a side note what do you think of Oracle Fertility HPT's?