I have 28day cycle had sex in my 1n2 day window how possible could i be pregnant and how long does sperm live in a vagina thanks ?

Depends on luck: If trying to get pregnant, and if lucky, a woman will get pregnant the first month. Many young, fertile women get pregnant in the first 4-6 months of trying... but one CANNOT predict exactly when. The less lucky will get pregnant by 9 months or so. If taking longer than 9-10 months, one can ask her doctor about checking for infertility problems. Sperm can live ~5 days, somewhere beyond the vagina.