Hi again,
I agree about it being tricky because it's your first relationship with a woman - but in a way it's almost easier to 'come out' when you're going out with someone- you don't need to use the words "I'm gay" - because that might not necessarily be the case anyway (I don't like boxes and labels!!), you can say something about being really happy at the moment because you're going out with someone and she's wonderful! Or something like that. Puts the onus on the person you've told to ask anything more or not. Even now after 14 years if I'm starting a new job I'll stick a photo of dp and ds's on the wall and just get it into a conversation - dp's my partner etc.etc. Much easier than the huge big "I'm gay" announcement..!
Anyway, take it at whatever pace you think is right - it'll all start to come together when you want to start introducing your girlfriend to other friends, and then eventually family (gulp!). And don't think you have to back yourself into a sexuality corner - I prefer the phrase 'flexible sexuality' myself (although dp would defnitely call herself a lesbian). Good job we're all different!