Anon,
Let me state up front that I'm not a mental health professional and this is only my opinion.
That said, you need to look at what part of it you "enjoyed".
You might have enjoyed the fact that someone (a woman in particular) took more than a passing interest in your discomfort and seeing it taken care of. The fact that your wife has this aversion to "anything anal" means that this was something you may also considered "dirty" so there were already some sexual connections inside your mind.
Another thing you need to consider is perhaps the enema tube simply stimulated your prostate. Take a look at the following websites about the subject:
http://www.mypleasure.com/education/sex ... ostate.asp
http://www.prostate-stimulation.com/
http://www.google.com/search?sourceid=n ... f+prostate
(Google results were included just to show how common this is)
As you can see, stimulation of the prostate is often a very pleasurable thing. If you reacted sexually to this stimulation, then you had a natural reaction to the stimulation. The fact that your mother was involved was understandably disturbing to you. You need to understand that you were not reacting to her, but to the act itself.
Are you a pervert?
In my opinion - no. You were simply a male having a standard reaction to physical stimulation.
Should your mother help you with future enemas?
Again, my opinion is no. This is not something natural and it sounds like you were uncomfortable with that idea to begin with and your mother basically bullied you into allowing her involvement. I agree with your wife that you need to see a doctor about this, but I also suggest you learn how to do this on your own.
I hope this was of some help.