suggestions needed

i started my period when i was almost 15 years old and from age 15-18 my periods were 14-26days long and id have a period every 2-8months and the cramps were so bad I couldnt get out of bed and the flow was so heavy, on my heavy days id have to wear an ultra tampon and change it every hour or id bleed through my pants, very irregular. i told my doctors but they never looked into it and just said it was normal. but when id tell any friend none of them could relate. I got on birth control pills at 18 and about 6months into the pills my period was regular flow and lasted 7-9days, I'm 21 now and 3months ago I went off my pills and have a 3day period late March and a 7day period mid April but havent gotten my period this month or may and according to this app im apparently 17days late I was told by age 20ish i wouldnt have irregular periods anymore by 2doctors, any advice would appreciated. Thanks x