Well here are my two cents worth, and by all means I am not at all trying to confuse, mislead, or add fuel to the fire, so I apologize now if I do so. But, on that note, here's my take on things.
1) A coffee enema isn't going to detoxify anything, nor is any other kind of enema really for that matter.
2) No matter what the commercials say, no you do not go around carrying 30 lbs of poop like the Colon cleanse, and other products of the like commercials claim you do. Will these products make you crap a lot, yep, they sure will, no different than Miralax or the other medications in this class will do. Even knowing just the basics of human anatomy and physiology, and I do mean the bare minimum of basics will prove these infomercials wrong.
3) As a medical professional myself, I can honestly tell you that enemas are NOT considered alternative medicine as a general rule. Maybe some solutions used for the enema could be, but I would almost bet my years salery that enemas are a part of if not almost all of any health care facilities standing orders for bowel protocol. So given this information, and taking it at face value, I would have to lean more towards the argument that enemas are usually "western" medicine. Or as I like to refer to the former and latter as quackery and real medicine.
4) Ladydoc is right the GI tract and the reproductive system are TWO totally different bodily systems, where unless you have a fistula, neither will ever meet the other, or for that matter effect the other. The only way an enema could even remotely effect a women, or hinder her from becoming pregnant would be what was in the solutions you were using in the enema itself. Again, this is basic anatomy and physiology here. Our bodies have a pH scale. If a man's pH scale is off whack it can damage or even kill sperm. With women, if her pH is off it will and can also kill the sperm once it's inside her. Honestly there are thousands upon thousands of things that could go wrong within our bodies that hinder a woman from getting pregnant, from both sexes. The more you read about it the more you have to wonder how our race still exists. So basically here, unless you are using a solution that will change either of your pH balances, enemas will NOT help a woman get pregnant, and once pregnant will not be harmful to the woman or the fetus......again, a disclaimer here, I say that with a grain of salt because if you are into things like wine enemas and other things of that nature, then yes, that could, would, and will absolutely potentially cause harm to the fetus. We had a court case here not too many years ago when the mother was heavily into alcohol enemas, she did them a lot, and probably could tolerate a lot more than most. Long story short, her baby did survive, but was mentally retarded and had fetal alcohol syndrome. Her lawyers tried to get her off stating that she never drank any alcohol, but their expert witness, a medical specialist on the topic proved that actually taking alcohol rectally absorbed quicker and was absorbed more rectally vs orally. She went to prison on second degree murder. So you or her could take your basic tap water or light soapy enema till the cows came home and it would neither help nor hinder her chances of conception.
5) It does't matter how much poop a person has or doesn't have, still has absolutely NOTHING to do with whether or not a woman is going to conceive.
6) More so then men it seems, women just are not into the whole enema thing like men are. Yes, there are tons of women who love them and swear by them, then there are 200 tons of women who just don't and will never like them, then there are an eighth of a ton of women who started out hating them, afraid of them, didn't like the feelings at first, but have somewhere along the line learn to accept them, deal with them, and even at times enjoy them. (this is the group I fall into). Your wife is probably part of the 200 tons who will never like them. That's okay, who cares, no big deal. Trust me, and I am speaking to you from steadfast and hardheaded woman. If we say we don't like something, then we don't like something, so deal with it, you probably won't be able to change our minds. If we are sitting on the fence post, trying to weigh the pro's and con's, to try it or not, the more you talk about it, push us, nag, hint or whatever is the quickest surefire bet way to make us step onto the opposite side of the fence in which you were standing, or were hoping for us to come. We hate being pressured, or bullied into something we don't want to do, or haven't made up our minds about whether we want to do it or not. So your best bet here is to not mention it again. Maybe the better way to go about getting her involved is to see if she would enjoy giving you your enemas, and then leave it at that.
7) I don't know how long you have been trying to conceive, but most fertility doctors want you to try for anyplace between 1-2 years on your own before seeking help. You can buy over the counter test kits that will tell and help determine when your wife ovulates. Another good idea is to get a basal temp first thing in the morning before her feet even hit the floor, and I am not trying to be funny or kinky here, but her temp really should be taken rectally, as it is, (no cliche intended here), but it really is the most accurate. They sell special thermometers just for this exact thing actually. I can't remember if it's when it goes up or goes down it means she's in her window to conceive. Also, don't wear tighty whities, and do not masturbate. Lay off the caffene, that also can effect things, and I believe it has to do also with the pH balance and I believe things like coffee raise the pH balance to unacceptable levels conducive for conception. I could have those mixed up, so please do your research on that.
After all this fails, and I hope that it doesn't, then you need to go and see a fertility doc who will most likely put you or her rather on clomid, or another drug in that class.
Good luck.
Mashie