My period

I've been trying to have a baby for a whole year now . I had a IUD for 3 years before having it removed. My husband and i have been trying since I've had it removed. The only problem i seem to be having is that my periods are extremely off track and NEVER fall on the same date or same time . It names it extremely hard to tell when im ovulating . My last period was on May 4th and haven't received one since I've took 5 o pregnancy test all say no :( how can i get my periods on track .