Trying to fix this marriage

So I am running out of ideas on what to do with my marriage. I have been with my wife for 19 years, married for 16. We got together when I was 19 and she was 25. We have 2 wonderful daughters, house in the suburbs, 2 dogs, good jobs, etc etc. What we don't have is much of a connection, or passion, or sex. We've had this issue off and on for most of our marriage, but it has gotten progressively worse in the last few years. I will admit that 10-11 years ago, I did have an affair, and it was with her best friend at the time. We went to counseling and we seemed to have worked past it. It does not ever come up in our conversations, other than the occasional reference to her castrating me if I would ever do it again. I work long hours, I always have, but I try very hard to put in as much home time as I can. I think I am a good father, I spend a lot of time with my kids, and try to be there for them when they need me, and give them space to be themselves when they don't. My wife and I have sex maybe twice a month, and it is always the same, a morning quickie before we get up. I always have to instigate it, and have to try probably 8-10 times before I get to the morning where I get a response. We don't go to bed at the same time, she often falls asleep on the couch, or will go lay down with one of the kids and sleep with them for most of the night, although she is usually in bed when I wake up in the morning. The only thing that seems to hold her attention anymore is the computer. Whether it is facebook, games on facebook, or watching TV online, she is at the computer from the time she gets up in the morning until she goes to work, and from the time she walks in the door and puts on the tshirt and sweatpants until she goes to bed. I recently tried to talk to her about the fact that I felt there was something missing in our relationship, and she agreed, and we tried to talk about it, but since that point, she has no interest in anything but the computer again. We even went out to dinner to celebrate our anniversary, and we hardly spoke the entire meal. I have tried everything I can think of, and from all the reading I have done on here, its all been wrong. I've tried to talk about my feelings, and my needs. I have taken to doing most of the housework and laundry and cooking. I have tried every romantic thing I can think of, and I'm out of ideas. The only comfort that I have found in a long time is this forum, where I find out I am not the only one in this spot. Any advice is welcome. I am reaching the point that I may just call it quits. I don't want to get divorced, I love my kids so much, and coming from divorced parents, I don't want to see them go through that, but I am seriously unhappy, and don't want to live that way anymore.

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