Hi Dr. Purushottam welcomes you to HCM virtual clinic! Thanks for consulting at my virtual clinic. I have carefully gone through your query, and I think I have understood your concern. I will try to address your medical concerns and would suggest you the best of the available treatment options. With your history it appears that you were not on birth control pills and you had unprotected sex. It always involves risk of pregnancy. Usually I suggest to take PLAN B or i pill within 24 to 72 hours of unprotected sex act. This usually helps to prevent pregnancy. Just starting contraceptive pill may not have pregnancy prevention effect as that of PLAN B pills.You need to take 5 low dose pills at a time - 2 times with interval of 12 hours,to equal the action of PLAN B. This leads to lot of stomach problems. and starting single pill daily will not be of use. In view of your irregular cycles, I will suggest you to get urine pregnancy test after 3 weeks of that sex act. Even if it is positive ,you can opt for termination with pill safely till 9 weeks of pregnancy. I hope my answer helps you. Thanks. Wish you great health. Dr Purushottam S Neurgaonkar