Chart. Get a book called taking control of your fertility. As you get older, your cycle changes. Charting will help you figure out exactly when you ovulate.
I'd say stop trying, just have fun. That's when you'll least expect it to happen and it will, don't stress and good luck!
Also looking into ovulation kits, is a great idea!! We are expecting our 7th child, ovulation kits have been successful for us! I also kept charts of everything.. premenstrual symptoms, dates of my menstrual cycles ,body temperature etc etc. I can definitely say, relaxing and enjoying the moment helped us so much!
Try using preseed fertility lubricant it aides in the sperm getting to the egg. there r countless positive reviews, and I used it to get pregnant. I'm now 19+3wks. Goodluck!!