I agree with Spade22. Irregularity doesn't mean conception is impossible but it could definitely make it harder or mean that something is going on (like not ovulating).
How long do you go without a period? I can go forever without a period and without a period I don't ovulate. I had to go with a fertility specialist. How long have you been trying?
If you arent having regular periods then you arent ovulating on a regular basis. Your best bet is to see your OBGYN who can determine if there is a problem and try to regulate your cycles.