No news is probably a positive sign. If you were a definite no-go they would tell you pretty quickly.

If it's dragging out it means they probably intend to hire you but just haven't fit you into a class yet. This may also mean that they have other candidates who they prefer over you, but will still likely get around to you.

Might also mean there was something in your background that they needed more time to resolve...but you'd probably already know if something like that exists.

Send them an actual letter thanking them for the interview, and re-affirming your interest in working there (if you didn't already). You should have done this the day after the interview, unless you decided it wasn't for you after all.