Shared my partner, my body rejecting intimacy with him now. Help! Why?

[nautilus]

Shared my partner with another woman, my body rejecting intimacy with him now. Help! Why?

After watching him have sex with someone else, something has changed. He keeps reminding me how much he loves me, but my body is not catching up with that fact and it ends up rejecting him. Our sex is not what it used to be because I can't open up and feel comfortable letting go anymore. Feeling very self conscious and self judgmental. Need your advice, guys. Thanks