Do not worry not necessarily the withdrawal bleed has to be there. Many of the females do not experience the withdrawal bleed and since you have taken IPill within 1-2 hours of having sex it is completely fine and you do not have to worry for getting
pregnant. Regarding your periods that is also very natural and most of the women in today's time get a regular periods. Some pathological causes which cause irregular periods are PCOD thyroidism etc. My suggestion would be, download an app for keeping a track of your periods which will give you an idea for a regular you are.
Next Steps
visit a gynecologist of the problem process and get an ultrasound abdomen done.
Health Tips
avoid all kind of sexual activities for now till you get your next menstrual periods