Ovulation

Help. I took the depo shot once in 2012 then my cycle went back to normal the month I didn't redo my shot, last year in March, I went back and did the shot again, I was due for June, but I didn't go back, from then until now my cycle is off track and very irregular. Me and my husband is ttc since last year , I am afraid I am not ovulating because we have sex often and I never know the exact time of AF because it is irregular.