I had irregular periods also but I went to the doc told them I had been trying for a year and they help figure out what is going on they gave me a some pills called clomid in March a month later I found out I was pregnant.
I would first try an ovulation kit. It'll tell you when you're most fertile. I always have had regular periods and it still took us 6 months to get pregnant.
I never had regular periods. My fiancé & I never thought either one of us could have a baby. We tried for a couple of months, then stopped. As soon as we stopped, BAM. I'm currently 17+6 weeks! It's always when you least expect it. If you're on birth control or use condoms, stop. Goodluck!