How can I really tell that im ovulating

I've had the Depo shot once in 2011-2012 and then I had a child followed by two abortions.....I am no longer with my husband and I am in a relationship with someone else....we actually got pregnant last yr and I decided to abort that child as well for personal reasons...after that I decided to get the Depo shot but discontinued getting it because I had bad effects the second go around....but since then I've had extremely heavy periods etc........I'm curious if once I do decide to add to my family will I be unable to and how do I know when my body is back on track and I'm ovulating again?????