period 21 days apart

k so i’m just gonna be straight with this lol. my boyfriend is coming to visit me at school next month and eve says i should be getting my period the week after but for the past couple months it’s been 21 days apart instead of 28. which would mean i have it the whole week he’s here rip. y’all i haven’t seen him in months 😩. anyone had this and know if it stays that way or goes back to normal?

also i’ll be going on birth control two weeks before 😏. would this mean i won’t get my period until the 28 pills are up?