Thank you guys for your input. :)
20 percent chance of pregnancy per month with sex that was unprotected (including condom error). Wait 2-4 weeks then take a pregnancy test with your first morning urine
There is always a chance you could get pregnant. 4 months is a long time for your periods to get back to normal. Your DR will be able to advise you - however my DR said when I came off the pill it could take up to 6 months before being regular again. Take a test in about 2 weeks time just to see. However, I would make an appointment with your doctor or family planning clinic to find out more about your cycle.