Have you had any testing done. I had irregular periods since starting my period. I was later diagnosed with poly cystic ovarian syndrome (PCOS). I had to use clomid to assist with ovulation. If you have been trying for a while and are having irregular periods it might help you to talk with your dr. Using ovulation kits might help pinpoint when you do ovulate, but if your irregular you may have trouble ovulating regularly. Hope that helps.
Yes, because it would be harder to pin point when you ovulate. If you do have irregular cycles try using Opks that is a way to find out when to have sex to better your chances