Help in calculating pregnancy weeks!

Anyone can help calculate my pregnancy weeks? Hello! I’m currently pregnant according to the pregnancy test kits but I’m confused by how I should be calculating the pregnancy weeks because my period has always been irregular (usually 40+ days) so it should be inaccurate to calculate based on last period? According to my period tracking app I should be having my period on 12 March Some info… my last period was on 26 January. Intimate on 25 Feb & 10 March 😂 First tested very very faint positive on 17 March with clear blue ultra early. Took the clear blue digital test 20th March and was 1-2 weeks pregnant. Took again on 27th March and it already became 3+ weeks pregnant 🤨 Any inputs will be appreciated! Thank you.