Advice

Thank you, Dr.....??

Nothing like writing several paragraphs about the all together too obvious.
Ah, thank you for sharing. Most of the replies seemed to have the lifestyle as the agenda and not the well being of the poster. So, not a doctor, just another noncom, like yourself.
 
Guilt and shame are the great ruiners of many relationships that would otherwise be full of wonderful experiences. Your feelings are very normal for pretty much everyone. What you seem to be missing is not the why, but the why for. Your guilt stems from something much deeper than the act itself. Many people find the desire so overwhelming that they place their base morals in a box, then after the dopamine and joy pop, those base morals return in the form of guilt and shame. It is not always religious, but how we are raised to view ourselves and others. Man and Wife have been traditionally monogamous for so long, that the entire sphere of the marital relationship revolves around the guilt and shame of violating this social ideal. The reason I focus on this instead of "focus on your wife's pleasures...look out for insecurities...address guidelines" is that you are expressing guilt, shame, and regret. Only you can identify why these emotions are associated with your choice to participate in something you both clearly enjoy. I would say look back, deeper and into your base morals and see if you can address those and with the help of your wife, guide yourself into a healthy appreciation for open sexual experiences, without the guilt, shame, and regret. Unless that is part of the thrill, and I am not kidding.