Anyone else worried about how your marriage looks to your children?

I haven't read or posted here in a long time, but this thought came to me today.  Your children's view of marriage is based on what they see from their mother and father.  And I'm scared to death that my kids are not seeing a very healthy relationship.  They are still young-5, 3, and 1yo.  I'm not wanting a divorce, there's just no way I can do that to my kids.  But my ADD husband and I just can't be showing them how a good, healthy marriage should be.  He is constantly letting me down, ruining my plans, not being on my team when we discipline the kids.  And the fact that I feel completely emotionally detatched from him, I can't even pretend to show him true affection or put on a front that I'm happy and that we care for each oh-so much.  I literally cringe sometimes when he shows me affection.  I know that sounds awful but I just can't help it.  When those feelings are there, I simply cannot fake it.  He has no complaints about me really.  I'm simply not close to him-you know that ol' talking to a brick wall thing-and I can't fake it in front of my kids as much as I may try.  I love him, and it's not like we scream at each other in front of the kids.  But I know they're not seeing what I want them to see and I'm scared to death this will negatively affect their views on marriage and affect their own marriages in the future.  I'm not complaining about my husband himself, but just-how can I help my kids know what a good marriage should be? 

By the way, he refuses to do anything about his ADD let alone learn anything about it.