Thanks for your query.
Firstly, with irregular cycles, and in the absence of periods, if you had unprotected sex, then yes, there are definitely chances of pregnancy.
Please ask your doctor to first confirm that there is no pregnancy by ultrasound and blood test.
you can then take progesterone tablets
for withdrawal bleed.
After the withdrawal bleed, you can start OCP from the 1st or 2nd day of the period.
Have thorough evaluation to rule out polycystic ovaries
, endometrial hyperplasia
, thyroid hormone imbalance