Trouble conceiving

Jennifer
I've been having trouble conceiving now that I'm on my cycle again. My cycle has never been steady. Could be from 19 to 27 days. I was lucky and had my son cause I had just gotten off Iud I had for 4 yr. Now trying normally and with prenatal I'm not having any luck. Especially since cycle never the same so hard to tell when I'm fertile. Any advice?