You're not a failure, but it might be unrealistic to hope that he could leave a sex-starved marriage completely for four months and yet it would somehow get solved in his absence. You didn't have the other half of the problem with you working to solve it, so you weren't going to solve it. Doesn't mean you can't solve it now, but at some point you would need him working with you.
That's part of the reason you're encouraged to work on yourself, doing 180s and working on what makes your life better for you (especially if he's going to be gone for a long time again.) That isn't necessarily intended to solve an SSM by itself (although it can make a big difference if you commit to it) but it has the advantage of doing a lot of good regardless of whether the SSM ever improves or not.
I do "hugging till calm" from Schnarch without ever having actually explained it to my wife. I just started doing it, and one day she relaxed into it. Ever since, she responds to it with relief, but she's never asked about it and I've never felt the need to give her the clinical explanation of the theory behind it (I do learn.) When it works, it's like taking a power nap . . . it's restful, refreshing.
Did you talk to your husband before he left about what YOU expected to work on while he was gone? If not, that's OK, I'm not beating you up, but if he expected you to do some kind of sex-acceptance exercises for four months (man, that's a long time!) are you perhaps more nervous about dealing with his expectations? Are you afraid he's going to come home expecting his wife to have flipped the Sexual/Asexual switch in his absence? On the one hand, that's not giving him much credit; he should realize that he can't solve a problem in his marriage by leaving and hoping someone else will solve it for him. At some point, if your goal is to save this marriage, you're going to be forced to have a serious talk with this man and explain what you want and need from him. That doesn't have to be the first thing you do, before the work you do for yourself, for instance, but you can't save the marriage by yourself. Don't fall into the trap of accepting that expectation; to the extent that you're working by yourself, you're working on yourself and things for yourself.
I might sound like I'm beating up on him, but I'm really not doing that either. It's just that what he's trying to do is dooming him as much as you. There Ain't No Such Thing As A Free Lunch.
