What has caused you to switch off?
You do sound bored and fed up with life in general, and perhaps this dissatisfaction is being placed on your DH to some extent (although he may be very boring, I don't know).
I think those early years are tough, 3 is still very little and if you are anything like me, you feel wrung out from being touched and pawed at by a little child and I think for me at least, this meant I became less interested in being touched by my partner, as it just felt like another job to do. This has lessened over time, as the children have got older, and by prioritising intimacy.
I also think it is normal to fall out of love at some points in a long marriage, I have certainly had periods of several months of not liking my husband very much and finding him irritating, but equally swings of really falling in love again. Obviously without the upswings, there wouldn't be much point.
You do sound fed up and dissatisfied- SGB's question is a good one- do you get time to yourself, to persue your own goals and interests or are you a bit subsumed under all the drudgery that goes with having a small child/working etc.
Another way to think about it - what would you gain if you left your husband? Sounds silly, but is there something about that life you are longing for that he really could not provide, or is this just a temporary lull at a rather hardgoing tired episode in your life.
I don't know the answers, but if you still like him, have fun together, get on, this is worth asking these questions over.