Dan: Wait, you're worried about freaking him out for no reason? This is a huge decision, and it will exact an emotional toll, whatever the result. If you decide to keep it a secret from your Really Great Guy (R.G.G.), how can you reveal to him anything more than your most superficial self? Granted, some men don't want much more than a woman's most superficial self. But is this the kind of man you want? No good can come from waiting. I see four possible scenarios:
1) You grow closer, but don't sleep together. Meanwhile, the A.I. works, and you have to drop a true bombshell, at which point he freaks out and leaves you.
2) You grow closer, sleep together, and you find yourself pregnant by you're-not-sure-whom. A year later, you, your baby, and your R.G.G. appear on one of Maury Povich's paternity-test segments, at which point all of your friends freak out and leave you.
3) You grow closer and fail to get pregnant by R.G.G. or A.I., but he freaks out and leaves you anyway because, let's face it, a great guy can probably tell when a woman isn't being straight with him about the most important emotional issue in her life.
4) You don't grow closer. You don't get pregnant. You break up with R.G.G. and remain alone and childless. Nobody freaks out, but it's still kind of depressing.
There is another way! Take R.G.G. to a nice restaurant and, when the mood is right, explain to him where you are in life. Tell him you've always wanted children but time is now short (make a joke about not putting pressure on him), and so you're looking into doing it on your own. Tell him you're ambivalent about it and still looking for the right man (make another joke), and see how he reacts. If he is indeed a really great guy, and if the restaurant is nice enough, he probably won't freak out on the spot. If he says, "But I want to be the father of your baby!" you've got options. If he says, "I've never wanted children," you've cut to the chase. If he says, "Tell me more," you can both move forward—or not—with full knowledge.
Best case, he'll respect the difficulty of your decision, the agony of your admission, and the generosity of your spirit, and you'll both have my admiration. Or you can put it off until you and R.G.G. are on Maury Povich's couch, trembling and weeping as he rips open the envelope. The choice is yours. But if you choose the latter, be sure to let me know so I can set my TiVo.