Have you been charting? It is a very good way to pinpoint your ovulation.
If you haven't I recomend
www.fertilityfriend.com, if you just want the basic chart for ovulation it is free, you can pay a very reasonable price and have a more advanced chart if you would like, but the free one is perfectly fine. They also have a free course you can take that is super helpful in teaching you the ins and outs of charting and recognizing ovulation signs!
Also, you can get a Clear Blue Easy fertility monitor from Ebay pretty reasonably and often they have test sticks included with them!
Hope that helps