OPK's after birth?

I know the hormone that OPK's pick up is always in your urine which is why you should test at the same time each day for consistency. Just wondering if that hormone is present in higher levels after birth and if it effects the test results? I'm wondering because on christmas day I had loads of WCM and today a huge blob of EWCM and am wondering if I am going to ovulate and then get AF back in a couple of weeks and thought I'd do an OPK if the test results would be accurate. I am breastfeeding DS every 2 hours even through the night so thought it'd be unlikely but I have had AF type aches for the last couple of weeks and was chatting to my mum on xmas day and she said she got pregnant again while breastfeeding my 6 week old sibling :o