I agree with Jessica, never presume to know what someone is thinking about you - usually you are only substituting their thoughts for your own. That way lies paranoia, let me tell you!

That sour look on their face might be gastro, that smile might be remembering the sexy time they had last night, that laugh might be a remembered joke, etc. Even when people tell you what they think how can you be sure they are being truthful? Unless you have clear evidence to the contrary you can't, best not to use up excess energy worrying about it. Personally I just presume that people know I'm trans. I met a woman through a work meeting two weeks ago and met up with her this week for a chat in a cafe about work stuff. If she realised I was trans she never alluded to it, it wasn't relevant to the conversation so I never raised it. I'll admit a part of me was absolutely one million percent dying to know if she knew or not, but since it wasn't relevant I was able to ignore that.
What's it like to pass? Awesome!!
I built it up, first few attempts were successful but low on the difficulty scale (even though it did involve going out into public, catching public transport, etc) and I just kept making subsequent efforts more difficult but as relevant to real life as possible to build up my confidence and my skills. See it doesn't matter if you can pass in nightclubs, it's awesome if you can, but life as a woman doesn't revolve around looking like you're at nightclubs 24/7...it's in going to work, catching the train or bus, going shopping for food and clothes, going to cafés, dealing with clerks at banks, etc. That requires a very different presentation to the nightclub look, clothing and makeup is usually much more subdued. That's where and how you need to be able to pass if you ultimately want to being living and passing full time as a woman.
Good luck, and welcome the forum!