None of this sounds good in any manner.As has been said before, you yourself need to start out with an M.D.. Your libido level is unusually low. There are numerous things that can adversely affect libido including a handful of prescription and over-the-counter medications. You really do need to get this thoroughly evaluated by a medical professional. In addition, the next factor is marital counseling. Fantasies are just that. If a partner wants to stray from a committed relationship to explore fantasies especially at a time when numerous health considerations and STD's are out there lurking like a "mine-field", it indicates a deep seated dissatisfaction with what she has so far experienced.The next factor that concerns me most with regards to your own future is the use of any device that would artificially create a situation where your own penis would be the least desirable alternative. If you were to substitute dildo's. strap-on's, sheaths, or any of the rest, what is the incentive to want to have sex with you? If you do that, you certainly are going to greatly compromise your own enjoyment of an intimate act shared between a married couple. You would only be reinforcing the desire for increased dimensions instead of learning to make use of what you have to the best degree in order to satisfy her.The final thing that also bothers me is that when an individual starts talking "size" especially after a committed relationship, this would be an indicator to me that the individual looking for "larger" has already experienced "larger", compared you to the fellow with larger dimensions and had found that to be far more desirable, and more "important" to her than the organ she married. Now, the next problem for her would be in that situation if it had happened....... The other guy was better in bed.....what do I do now? This has got to be an extremely painful time for you and it has with little doubt shaken you very badly. The questioning of your masculinity would as a normal effect make it very difficult to achieve an erection with your spouse and it would create all kinds of psychological pressure to perform.All of this forces you as a male to try and live up to something that right now seems impossible.I would also take a wild guess that you, as you were growing up, lived in a home were sexual intercourse and relationships were never discussed. Basically, you have had two problems. The first has been the frequency of your desire, and the second is quite probably your lack of knowledge on the subject of intercourse, and a probable situation where you were able to ejaculate, but rarely if ever in your marriage brought your wife to orgasm. Sorry pal, it may hurt a little, but my impression from what you have said for some reason says that this may not really be your fault. There are such things as sex therapists, and this may be another avenue for you to at least investigate. This is a marriage that is already in deep trouble. Both you and your wife are hurting in different ways.After what has been experienced here by both of you it is going to take an absolutely heroic effort on both your parts to save this marriage. I really hope that you are able to do so and wish you the best of luck at trying.