What to do so much in love it hurts

Well were do I begin, I have been married for 4 years been in love for 7. I just found out that my wife had an affair with my relative that I had let move in with us after he got out of prison. See i made a mistake I knew they had a history, They had dated long before we got together and he treated her very bad and damaged her self esteem. I talked to her before I allowed him to come stay with us to be sure she was alright with him coming and that there were no feelings for him, She assured me that there were none. I only allowed him to come because he had no one else to turn to. well he was there 2 months and i found out that he was telling her how much he loved her and next thing she was telling him she loved him too. they slept together in our house when I was asleep, they were texting each other every day, they were planning a life together she asked him if he could love our son as his own, etc. then one day she stayed at her friends house because she was going to leave me. the next day she told me some of the truth and I kicked him out. since then she has slowly told me the truth and there was 2 other affairs she had. now we are in counseling and trying to rebuild our marriage but I cannot get the images out of my head. This woman was the love of my life, I know everybody says that but I have been married twice before and lots of relationships and this was something I have never felt before, we have never argued always told each other how much we loved each other every day of our lives. I cannot stand to be away from her and she says the same about me. she says that she was under so much stress from a failing business that she owned and didn't feel she could come to me is why this happened. and he was constantly telling how much he loved her. I am so lost as I still love her with all my heart and she tells me this was a huge mistake and she will do anything to save our marriage. what to do, what to do we have a beautiful 5 year old child that we both adore.