hi i had gone through your query and understand your concerns. i would come up with two most possibilities to fit your condition of irregular periods
1.first possibility is,PCOD ;POLY CYSTIC OVARIAN DISEASE
is one of the main factor of infertility
in females nowadays. Women with PCOD have High levels of male hormones (androgens),An irregular or no menstrual cycle ,Many small cysts (fluid-filled sacs) in their ovaries (although this may not always be the case).due to above reason the OVUM CANT BE RELEASEDultrasound
scanning for pelvis may confirm the diagnosis
2.second possibility is,HYPOTHYROIDISM;confirm with blood test
for thyroid profile.
without treating the cause of the irregular periods you cant be pregnant.
treat the cause but not the complaint.
wishing you good health