Big mistake

Been really upset. On july 17th around 4am i had a threesome with with my husband and his bff ( were all std free) i was super drunk and don't remember a thing. Messaged the bff the next day he swears he didn't cum inside me. Find out im pregnant on August 5th. Have an ultrasound and she said i got pregnant on july 28th. Now my husband says its not his. I just wish it never would of happened. It was my bday and got to drunk. I blacked out