ovulating while breastfeeding?!?!

Shelby • TTC #2!
Sooo I'm 9mpp. Hubby and I are ready to try for #2. I'm still exclusively breastfeeding my son, but my periods have returned and everything seems pretty regular. I decided to start tracking my ovulation to get familiar with my body again, but I've been getting bazaar results! 
Feb/March: positive OPK CD 17 and CD 24.. period of CD 30
March/April: positive OPK CD 28, period CD 30
April/ May: currently CD 24 with no positive. 
I am so confused!!! Can someone help me out?!?! Anyone have experience with ovulation and breastfeeding??