6th or even more senses? Perfectly possible. Senses which other animals have include magnetic fields, electric fields, seismographic sense, electromagnetic spectrum outside the visible range, pressure gradient, chemical gradients of many sorts, in fact anything that produces a physical effect. I suspect we are sensitive to many of these, but vestigially such that the signal is lost in the noise and has in evolution not made sufficient difference to us to be pursued. Anyone is free to devise their own tests; it's only a few years since a fifth kind of taste was proven.

Also remember that sensations of all sorts are highly processed before we become aware of them. You probably NEVER have a raw sensation. Before you know what you've sensed, it's been catalogued, put in context, and loaded with meaning.