Relying on your passport not being checked isn't a great idea.

Generally speaking, once in the Schengen zone, your passport isn't checked between other Schengen zone countries (although it can be). Also bear in mind that the restriction isn't just "90 days", it's "90 days in any 180 days", to prevent you doing a short hop over to London and back to start again...

Either you need to get hold of a visa (which isn't a simple process by any means), or you need to mix your travel between Schengen and non-Schengen countries. Do you know where you plan on visiting?