I find mpreg confusing and distasteful too -- not that I like preg fic very much in any position on the sex & gender spectrum.

I've read three that ever made the least bit of sense to me, one mpreg Viggo/Orlando by chaosmanor, one mpreg Orlando/Viggo by jasmineskie and this mpreg Elijah/Dom by randominity: You Say That Like It's A Bad Thing

(whoops, bad link there, fixed now)