My husband told my sister he loves her and another time told her he has feeling that he can't seem to get over

Ok everyone here it is... I have been married for 28 years and have 4 married children and 6 grand children, about 20 years ago my husband told my sister that he has feeling for her that he can't seem to get over for her during the 20 years he was caught sneaking into her bedroom in the middle of the night ( claiming he seen a mouse go into her room but he was caught picking up the blanket that was on her) there was a few other things that happened as well, but the latest issue started about 4 years ago, he once again told my sister that he loves her and then opened a secret email account and told her to he it out she never told me anything at the times those issues happened until one night he sent her a text message and told her to call him blocked that's when she decided to let me know wheat was going on. But by looking back I remember a time he was talking to her husband on her phone when she came over one day and he looked through her text messages and noticed she was texting another man and cheating on her husband. Right after that he started bickering about small thing with me, a few months passed when my sister was the talk of the town and family about her love affair with this person he then became very uninterested with me and the normal home and family issues, he also complained a lot about her big love affair, ( I told him at one time why does it bother you so much about her affair) don't know how I didn't see it at that time so we went to la for about a year and half, he kept complaining that he is ready to come back home and started saying that I was having a affair also we had many arguments and he was always looking for something, checking emails, cell phone records etc, so he continued this for the past 2/12 years but during this time he put a thing on the pc and was always checking where I went on the pc, every few weeks we would argue about something he seen on the pc or phone I would have to prove everything to the point and if I didn't it was true, so then I suggested a lie detector test to prove I am not have a affair, oh but big thing I forgot to tell all of yous is that the person he claims the affair with is the person that is my sisters lover, I told him that we don't associate with this person of his family where is this big affair coming from, I don't go anywhere alone and when I do it is for 15 to 20 mins, so I passed THAT lie detector test about this famous lover or any other man, during this time he has thrown me out many times and then for some stupid excuse or reason I would come back for one thing or another, or as he would say try to work it out..so as the normal routine he would start every few weeks and I would have to prove myself, so he wanted another lie detector test and I did it once again I passed, then a few weeks later he would start again throw me out and I would come back( thinking I can't throw away a 28 year marriage hoping that he would open his eye, my som was in the hospital and we were going because he was having test done and he told me to leave ahead of him and he will catch up when he's done with business, on the way to the hospital I spoke to him and other family members as well, that night he woke me up at 3 am asking me where I was today I told him everywhere I was and he told me I was lieing pulled me down the stairs by my hair and started hitting me,showing me a tape recorder that he placed in the car that morning with out me knowing and saying that I met a my sisters lover, I ran out of the house crying and shaking looking for help, finally the police came I took a few things and left. That was in 8 months ago, I have begged him to have the recording enhanced to see that it was him I was talking to on the tape and he completely refused, through out this time I also told him that I felt that he is in love with my sister because he is claiming my affair is with the same person and he is just looking for a reason to get back at him, well finally he did the tape and sees that it was his, and now tells me that may be his problem about my sister, so I am looking for help with this problem that I have been going through for ever it seems like, I really feel so stupid for always coming back and even staying with him after the first time he told my sister he has feeling for her that he can't seem to get over, he is now willing to go to a Dr for help on his trust issues and he says possibly my sister issue, I don't know if there is help for him about my sister if that is true, and don't really know if I can stay after alllll that and if it is about my sister, so I am asking for help on what type of Dr would be helpful and opinions if what I feel is right or not, so sorry about the long problem Thanks for listening Really lost.