Ovulation postpartum? Would it go back to 14 days after period?

Hi girls... I'm wondering about ovulation postpartum. My little guy is 7 weeks old (time flew). I'm currently on day 3 of my first post partum period.... For natural family planning purposes I am trying to track down my ovulation. I will definitely use opk's, but I'm curious if anyone knows that it will be 2 weeks after the period like it was before I got pregnant? I have a friend who claims it can come anytime and takes months to get back to the 2 week schedule... That seems odd to me. I know my cycles can vary, but I thought the length from period to ovulation was always 2 weeks...? Thank you!