I was going to get mirena after my d&c to remove a polyp but my endocrinologist says mirena is not good because i have pcos. she says syeda better. y?

Both are good: Both are reasonable options with advantages. Mirena is highly effective and does not require daily maintainence for up to 5 years. Most have light or no menstrual cycles which is a nice benefit. Theoretically but unproven the Progesterone could suppress endometrial polyps but polyps are rare at age 20. Birth control pills would regulate your cycles. Neither will “fix” PCOS.