Karen, Karen, Karen! This is going to be a 2x4...not on the DBing but on the attitude!
What brought you to the conclusion that you cannot do this? What part of this is not working for you? WHAT doesn't seem to be happening? The answer to either of these questions cannot be "all of it"; "I don't know"; "Just because" or anything of the sort. Put it down in the black and white...not the flowery words for sadness...the nuts and bolts of the PROBLEM.
Your husband is a grown man, and he is capable - as you are - of making his own choices. AND he is choosing to stick this out with you. Don't discount his ability to make that choice. Instead, make yourself a person that YOU want to be. Because I don't see this as a problem with the relationship you have with your husband. I see it as a problem with the relationship you have with yourself.
To walk away from your marriage right now would be the easy road. It is easy to play the martyr. It is harder to do something about it. However, doing something about it is going to be a lot more fulfilling in the long run.
You can't say you've tried everything. There are a million things out there waiting for you to try them. START. Post your goals on your refrigerator, in your car, in your office, wherever you speak to your H. Force yourself into a healthy attitude, a healthy lifestyle. If you backslide, pick yourself up and keep going. BUT DON'T GIVE YOURSELF THE OPTION TO QUIT.
If you feel that medication would be beneficial to you, then I encourage you to seek the means of that. But it is a tool, not a solution. It has to come from you, Karen.
"It is not easy to find happiness in ourselves, and it is not possible to find it elsewhere."
--Agnes Repplier, writer and historian