@Morose11: First of all, I am sorry that you are dealing with this. You have every right to feel turned off, angry, and betrayed by this terrible surprise. Don’t beat yourself up. It is a big deal. I am concerned that this behavior is a manifestation/symptom of a larger mental illness.
Also, the big deal goes beyond the fact that he uses diapers and may be mentally ill: it is even more so the issue that he actively hid this fact from you for the last two years. That is not an easy secret to keep and certainly one that a spouse would need to be aware of. He betrayed you, and knowingly entered into your marriage with a big secret/lie. In many churches that is grounds for an annulment. You are not overreacting.
What also concerns me, is that this shows what is possibly evidence of serious mental health problems in his family line. He may not only have serious mental health issues, but it sounds like his parents may as well. Mentally well parents would not raise their child to wear a diaper as an adult if not medically necessary. It sounds like something is wrong with his mom too.
Do you want to have children? If so, you need to find out what mental illnesses may run in his family. Consider whether or not he is fit to parent, and/or if you want to risk passing those illness on to your future children.
Should you want to try and make things work with him, it is imperative that he see a therapist and psychiatrist. You may also need marriage counseling to discuss the importance of openness and honesty. What else don’t you know yet? I am terrified that he could have worse secrets than this.
Can you start by talking to a pastor or priest at your church? They will keep this in confidence, and can likely refer you to someone who can help you like a psychiatrist.
Finally, should you feel that you do not want to stay with him, don’t feel guilty for thinking that way. You are a victim in a bizarre situation. He clearly has a mental illness he has kept hidden from you. I almost feel that he took advantage of your innocence to help hide his secret. The fact that you didn’t live together, or become intimately involved before marriage made it easier for him to hide his problems. Had you not been so innocent, he could not have hidden this from you so well. I feel he betrayed you and took advantage of you.
In closing, the poop is bizarre but the least of your problems. Your new husband may be mentally ill, he may have other personal secrets and major issues he has hidden from you, and you entered into a marriage under false pretenses because he betrayed you.
My heart goes out to you and I will pray for you. God is with you- definitely talk to your pastor/ priest as soon as possible about this! You may be able to annul the marriage should you wish to do so.