I suspect that my husband is a narcissist. How do I know for sure?

Sarah,

Your concerns as you have stated them, seem to point out more toward your relationship, and the inherent problems that have long been in the making, and preceding the birth of your son.  These issues also seem to arise from not any possible personality disorder that may or may not be present as part of your husband's character and temperamental make up, but with more certainty, stemming from your relationship.  It also seems that although you have noted some critical issues to your husband, and your approach is now to make certain that there is a proficient intervention to enrich your marriage, your husband seems to favor a more superficial approach, with facile generalizations and paltry answers that clearly do not scratch the surface of the evident need.  His behavior is not necessarily typical of a narcissistic personality structure, but rather it is more avoidant and perhaps denotes what could be a masked concrete fear or a more abstract, generalized anxiety.   

My reason for not necessarily favoring an indication of narcissism is because I see no evidence of exclusive self-centeredness with grandiosity or a demand for admiration and service and an idealized self image, or grand schemes and associations to the exclusion of others, and designed to serve what could be an underlying fantasy of his greatness.  Instead, I see avoidance, denial, and possibly an inability to connect well with you, and possibly his son, and perhaps others too.  

I know that there are multiple personality disorder diagnoses that may be used to capture bad behavior or poor interpersonal skills, however, these uses by the general public are typically weaponizing diagnostic categories with little clinical evidence. Offering the diagnoses as a reason for multiple aggravating circumstances in a difficult relationship, event, or interaction, where there could be great suffering is not helpful, and it usually becomes part of what could be an ongoing problem that could best be addressed by a more thorough understanding of true underlying problems, and issues.

Given the above, I ask that you please consider the following, in order to perhaps best address a possible solution to what troubles you now:

• 1. Clearly define how your husband has consistently responded to all the alerts that you have signaled, announcing to him what may be all too obvious, stating clearly to him: "Our relationship has been at risk, for a long time, and in order to salvage it, we need to change our approach and response to one another so that we could begin once more to develop the intimacy, and partnership, that a strong couple requires." 
• 2. If your husband's reaction remains the same, and there is no probability of a change, then inviting him to therapy as an alternative to greater damage, like separation, could then be articulated, in the hopes that he may then relent, and start taking more remedial action.  In therapy, the obstacles that he faces in coming together with you as his intimate partner may become more clearly elucidated.  Relatedly, there could then be a prescribed set of actions that you can both be guided to take to ignite a new spark, rejuvenating your union.
• 3. If these actions yield no result, then it must be considered, that no change may be possible. If you remain with overwhelmingly unmet needs, alone, and your husband resolves to remain absent from an active marriage, then it is a matter of developing the preparation for next action steps that could lead to separation.

Finally, I will add that if these problems have been going on for quite some time, it is very useful to consider when these negative changes took place, and what may have happened between the stages of a good and satisfying union, and the initial moments when you began to experience his lack of presence, and vigor in the marriage.  These identifiers can point the way to what the underlying issues may be, and how the intervening obstacles may be removed to install healthier attributes to your marriage now.

I hope this is helpful in letting you appreciate not only what may have contributed to your dissatisfaction, but also how you, and your husband could look at a way to repairing what could be salvaged in your relationship, as a couple, with a young child.