I didnt know where to turn and this is such a delicate subject because it involves my family and it has already heartbroken my brother and my mother....but I do not know where to go from here. My husband has been unfaithful before, when I was pregnant many years ago, yet I forgave him and within our ups and downs we have generally been "good". For the past year, however, I have noticed that him and my sister in law sometimes look at eachother "differently" especially from her, but everytime I mentioned it to my husband he would say I was being paranoid because of our trust issues and past....sure enough I would leave it alone because it was just so horrible to think about. To be clear, I know they had a fling many years ago because they were friends before my sil started dating my brother. Fast forward to a couple months ago, we were out and I see my husband text her I love you, i confronted him, he denied it said that he meant to send it to me, but didnt notice he was sending it to her, I confronted her, she denied anything going on and said that only what happened in the past is the only thing that had gone on. Yet as the months have passed I noticed how mad my brother was at my husband, he wants nothing to do with him and they were best friends. After much, much asking and begging for the truth from my part and a whole lot of denying from my husband, today he finally told me that about four years ago they kissed a couple of times because my sil used to throw herself at him and that nothing else has happened after that. I found that hard to believe and I went to speak to my sil, who says my husband used to try to seduce her, and that one night years ago, drunk they kissed. Stories dont exactly match....she also told me she does believe the "ily" txt was meant for her, because earlier that night my husband had texted her "you look nice" and that he had called her, but that in many years time that is the only thing that has happened, and back then only the "drunken kiss"....my husband admitted to the txt saying she texted him first and he replied, that it was stupid and that he is sorry, but that he never tried to seduce her and that he has no interest in her. I am disgusted, heartbroken and honestly still in shock. We have been married 7 years and together 11, it has been a hectic relationship but I hhave always respected him and above all we have both been very loving. We do everything together, I am not working but I am a full time student....he has been supportive....but now with this I do not know what to do. My brother and his wife are trying to work on their marriage, I dont know that I can do that. I feel so betrayed, I begged him for the truth, I warned him beforehand about my suspicions and still this happened. Please I need some guidance, I know I must seem dumb, and that this should be common sense, i should leave him, but I am also considering the "other" life we had, which was such a good one. He wont stop crying and saying how sorry he is, it honestly does not mean anything, I am numb and just need to know where do I go from here. 

Sorry this is so long and for the lack of clarity, but I cant even think straight....thank you