Thank you for your very compelling and sensitive question.
Actually you are not alone in this regard.
Much of our desire is ruled by hormone levels. At age 46, on average, males have less than half of the testosterone levels they had at age 24. testosterone is, as you know is the hormone most responsible for male sexual drive (libido).
But there is more to this than just hormones. that is only part of the story. Testosterone levels are influenced by level of exercise and diet in addition to the decline associated by aging. Desire is also influences by the character of your relationship. For example:
How many positive interactions you and your partner have on any given day or throughout the week
How you treat each other
How you communicate with each other and how often?
How you feel about each other (influenced by all the other stuff).
How your partner is keeping herself up?
Current form of sexual release
You are on the right tract to suggest counseling, but you also pulled that option out of the mix by stating that your spouse will not attend. BUT do not discount the value of you attending on your own, without the partner. If for no other reason, than to try to learn new ways of communicating and influencing your partner in positive ways.
Your wife is also part of the mix, as she is in fact going through changes. She is loosing lubrication, but her desire may also be affected by loss of interest in you because of drinking and overweight, and general appearance. Her hormones are also beginning to be out of balance, though her testosterone ratio may actually increase.
Since she will not go to counseling, then you need to do the following as a couple (you can go without her as I already mentioned). Though it would be better to go with her; sometimes when she sees changes in you, she will then consider going.
1. You are already working on weight and drinking. let me suggest a program for you that will not only reduce weight but also encourage your body to build testosterone.
Go to the following website and enroll in their program of virtual men's personal trainer. (incidentally,they also have a program for women). This men's health program has a diet and exercise program that helps to increase testosterone levels and lose weight. I am currently enrolled in the Testosterone diet and the belly off exercise program. Once I achieve my belly off program, I will switch to the testosterone exercise program for a few months. I am 58 and I can happily report positive effects in my libido.
with the men's health you can be looking more appealing and attractive to your wife in 8 to 12 weeks....looking like a god as they say.
2. This will hurt: but you need to get rid of the porno for now. It may help with your wife at some point in the future to help you get ready for sex with her, but for now, to recover libido and attraction to your spouse, you need to get rid of it. The issue is based on the psychology of attraction in these kind of situations. Right now it is easier for you to get aroused with the porno, and to masturbate, getting quick and easy satisfaction. You need to give you body and mind a chance to get, well...horny, as they say, and then direct that energy toward your wife.
3. I do not know the level of your drinking, nor the level of interaction between you and your wife. BUT it is important to not drink instead of expressing your feelings; and when expressing your feelings, even angry ones, in your situation, you need to express them in a non-negative way. In psychology, some disciplines suggest if we are angry to express it, and to also show it; yet in other disciplines it is sufficient to simply express: I am angry, without acting out. In your circumstances, I am suggesting that you need to increase the number of positive interactions with your spouse every day. These include things such as self esteem building phrases. Maybe your are already doing this, but remember, the more positive interactions you have, the better it will be:
Warm greetings that are genuinely expressed
compliments first thing in the morning
acknowledging clothing that she is wearing in a positive way
Noticing some small thing about her that you never noticed before or has been a long time. (I just noticed luv, that you have the cutest way of tilting your head when you laugh....for example)
Maybe you already help out around the house, but do something unexpected: If you are not helping out, do so...If you do, then pick something like prepare a meal for her and the family one time. Do something unexpected.
Take her on a picnic
Ask her to dress up and go to dinner, out to a nice place
Take her dancing or to dance lessons. (dance lessons are good)
NOTE: during this time of building positive interactions, avoid direct arguments. Respond to anger with things, like: I understand how that makes you feel; Can I help in some way? I apologize, what do you want me to do different and so forth.
ALSO: Take away the pressure to perform; do not focus on having sex or lets do it. Just allow that moment to arrive on its own, however many days it takes. Just spend time having positive interactions.
4. Buy some lubricant such as KY jelly to have available by the bed side, so that when the moment comes, you will be able to help her with her problem of loosing lubrication. Then, because your erections do not last a long time, have longer foreplay...much longer.
5. See your physician to get some Viagra or cialus, which ever he feels will be best for your. I recommend Cialus, because it is longer lasting. BUT, you and your physician should decide.
6. Encourage your wife to join you in the exercise and diet program by men's health. Remember, they have a women's program as well.
7. Finally, you can not remove any guilt she may feel about herself; but you can for yourself. AND you can give her support in a way to allow her to diffuse the guilt. Guilt interferes with libido, as well as does stress. The exercise and positive interactiosn will do a lot to reduce stress. Not focussing on performance will do the same. For any feelings of guilt she may have; simply be a broken record over time...each time she might mention this, simply say words to the effect that you understand, and not to worry about it; ask her if you can help in some way? be supportive, and do not use words that blame or focus on her.