Will a Catholic church ask you if you're really Catholic ? How would they know ?

So to be Catholic, you have to be raised Catholic, baptised and confirmation and all that. So what I'm asking is if I start going to a Catholic church and taking communion (i know you aren't supposed to unless your 'officially' Catholic)will someone say something to me like the priest, asking for proof that I'm Catholic ? If anyone asks, can I just say, Oh just moved here but been Catholic all my life ? Or will people/clergy kick you out?