I have mild pcos, i have done 2iui s with three chemical pregnancies.i want to try another iui, how can i prevevent another chemical pregnancy?

Get tested!: If you've had 3 losses, it's imperative to be tested by a board certified reproductive endocrinologist before you try to conceive again! why didn't your doctor suggest this?!

Early miscarriages: Biochemical pregnancy (positive HCG hormone but too low to see a pregnancy on ultrasound) is either very early miscarriage or early tubal pregnancy. You need to be checked for tubal problems and polyps/fibroids in the uterus with an hsg, as well as tests for diminished ovarian reserve (low egg supply). After 2 + losses you should be checked for thrombophilias and autoimmune causes of miscarriage.