Terms and Conditions? As Clynton points out, it sounds like you are in stealth mode. But here's the thing - while it makes sense to be in stealth mode from the big players - if you are worried about your customer base "stealing" your idea and executing on it better than you can, you probably need a new idea. Because if its that easy to do, even if you launch first, someone else will copy it and you will have competition.
This is particularly true in healthcare where if you are doing a device of somesort, the whole 510k Predicate process is designed to encourage such copying
BTW if this is you http://rhea-mhealth.co.uk/ and you plan on taking this idea to the USA - you probably want to consider taking a look at https://ClearRoadmap.com. (yes it is our product but this is less about a pitch to you and more about the fact that you are stepping into some potentially murky regulatory waters since even though all you do is connect women to "experts" in doing so, you are holding, tracking, and potentially revealing personal medical information. And that is regulated in the USA).
ok - so that helps. I full well understand how important that "first impression" is in healthcare arena. So what I would do is set up a non-public site (ie one that does not have your domain name mapped to it) and then identify a handful of users you trust and approach them about giving you feedback. And if they say yes - email them the URL with the explicit and clear caveat that this is a temporary URL for feedback purposes only.
Then after getting the feedback you can just take down the site, or close access to it while you finish developing it. Once you are ready to re-open it, you attack the correct domain name to it and roll it out to great fan fare