nursing and ovulation.

I am currently nursing my 2.5 year old and we have just started trying this month. I got my period back 6 months ago. Due to the nursing we opted to use ovulation tests this cycle, and I am on day 18 and still have not ovulated. 
Anyone have any experience with this? What can I do? 
Is there still a chance I could ovulate this month? 
With our son I stopped the pill (which I had been on. For 10 years) and ovulated 14 days later.