Missing aunt flo

About a year ago my periods started to become pretty much non-existent I wouldn't have them every 2 to 3 months. Id randomly I get awful pain and three days later, start my period for three or four days. My husband and I have been trying to get pregnant for two years and we've gotten pregnant and miss carried once throughout this time. With my periods being so irregular, I'm nervous we may never get pregnant! How can I know when I'm ovulating without going thru 30 tests a month? Better yet, how can I get pregnant when I'm not even ovulating except for 3 random times a month. I'm feeling like throwing in the towel. The disappointment is unbearable.