Waalaikum assalam! Tahniah sangat! Yes, long cycles & late ovulation boleh affect due date estimation, apps biasanya assume 28-day cycle dengan ovulation hari 14, tapi yours is totally different so the dating bisa off. Since you tracked your ovulation properly (cycle day 28!), your actual dating should be more accurate based on when you actually ovulated, bukan based on last period je. I'd suggest bring your ovulation tracking details to your first scan so the doctor can confirm the due date properly, they'll do ultrasound dating which is the most reliable anyway. Congrats again on your Baby April!