I *really* understand the confusion about not knowing how to gauge your emotions. Been there, probably will be again. I still wonder if you might be moving a bit fast for your comfort level though, given that it's only been 3 weeks.
If I could offer some further thoughts... In my own experience, that kind of anxiety and doubt might be about myself OR about the other person. If I'm feeling a bit rushed into things (like disclosing the H), it might be because I fear losing them OR it might be because I feel they're pushing things too fast, or they're trying to pull me in a direction I'm not comfortable with, or *I'm* trying to push things too fast (afraid it's a flash in the pan and I want to grab what I can before it's gone).
I wonder about you meeting her family so soon, which is usually something people do once a relationship is more clearly established. It's a big step, since it's a bit of a declaration that you two are now "a couple" and now risk somebody's mother pestering with questions of when you're going to get married. LOL
You might give some thought about whether you two have your feet on the ground about the relationship in general, or if you're trying to ride a wave of elation. If this is "meant to be" it will "be" if you slow it down too, and in fact might increase your chances of it working in the long run if you do. It's just something to consider.
MovingForward made a really good point in Sophia's thread the other day about how it helps to have a plan about these things; a sense of timing that works for you and a strategy of how to approach it. You might think about giving yourself a specific amount of time (e.g., 4-6 weeks) or number of dates (e.g., 5-10) before you will tell her. That can help to pace what happens a bit. If you feel things are moving a bit fast before that time, you could talk to her about needing to take things a bit slower. You don't have to say why specifically, just that you want this to work and you don't want to hit burnout.
I don't think you should feel compelled to rush into anything about this. Believe me, I completely understand the anxiety of "If I tell, will the person reject me? Maybe I should do it now and get it over with." I have found for myself that if I can slow things down (in myself as much as with the other person) and allow a natural development to happen of getting to know each other, it really helps all round. It not only increases my chances of the person not running away when I tell them, it also helps to slow down my own reactions so that I'm more balanced and grounded when I do tell them. I'm also in a better position emotionally to deal with a rejection if that happens. OTOH if you find you just can't concentrate on enjoying her company because you're so worried about telling her, then you need to take your limitations about postponing into account too.
Anyway, all these are just suggestions and ideas and sharing what has helped me make that decision...all in far more words than are necessary (I'm not fully awake yet LOL). Good luck with this! Keep us posted how you make out with it and however you decide to handle it. And good luck with your lady!

I really hope it works out for you.
TheOneInFour