You feel this way because you had feelings for him and they don't just shut off because you found all this out. As Seesaw said, you dodged a bullet. Now it will take time to get over. Just when you feel like you are getting over him, you are bound to have feelings resurface. It's a long process but one everyone's been through. Take all the time you need and take good care of yourself. Just know he surely has lost a great person.