I had an episiotomy a month ago and dr said i could have sex after a month. no pain during sex why does it sting at the stitches after sex when i pee?

May be too soon: I typically recommend at least 6 weeks for sex after a tear on the vagina. I'm assuming your md examined you and felt the vagina was well healed. It stings at stitches because your urine is acidic and the area where your skin/vagina is still healing is sensitive to that acidity. The sex is likely causing some disruption to the vaginal lining, making a little raw. Let it heal and will do fine.