Hi there, yes you can get pregnant if you are ovulating and irregular period are not any kind of birth controll.If you are not planning to get pregnant then it is essential that you or your boyfriend take some kind of contraceptive
measure. Get a PAP smear
examination done to rule out any other cause of postcoital bleeding.You could try reducing weight with some sort of exercise regime as it will not only regularise your periods but also has lots of othe health benifits. Take care.