hello, welcome to healthcare magic.
you seems hyper anxious to get pregnant. first of all be relaxed. the more get anxious the lesser are the chances of regular periods. i read your q properly. yor periods are irregular since a year, so first of all stop all hormonal
drugs if u taking. and let ur periods come on whatever time its coming.
2nd thing is imp. consider ur 1st menses day as day 1. now frm day 10th to 20th are imp to have intercourse to get pregnant, follow this thing.
3rd tthing. try this schedule for about 6 months. even then u dont get pregnant then undergo proper screening tests by consulting the infirtility doctor. do not use ur own logics and relatives or frnds. if u r nder treatment for baby, tthen follow all instructions of ur doctor only.
test only if u pass more than 10 days of your expected date ( as ur menses is a bit late) have patience. u can conceive till u r menstruating. whnever u r pregnant, its elderly pregnancy so take care of it.