Sounds like things are going along very well!

Snakes are so fascinating in that they see, hear and smell so well using their senses quite differently than we mammals do. They may not have external ear openings but they do have the internal mechanisms of hearing and can easily pick up very slight vibrations through things like their lower jaw bone and translate that into information about something moving in their vicinity. Their sense of smell is amazing. That forked tongue can not only transmit information to the Jacobson's organ in the roof of their mouth but also discern such minute differences in amount of smell so they will know for instance that a prey they are tracking just turned right not left. Their ability to sense temperature (those labial pits are handy things!) is said to be as minute as 0.2 degrees difference. As far as their sight, some things I've read say they only see well through heat sensing infra-red information gathered by their other senses and their sense of sight as we know it is very limited, other sources say that they likely see far better than we know and are able to switch back and forth from full spectrum sight to infra-red with ease. It is definitely proven though that in the end they rely on that heat sensing sight for hunting far more than anything else (an especially good adaptation since most BP's in the wild would be hunting in full dark inside tunnels in termite mounds).

Funny side note here, I was reading about infra-red vision in snakes and one thing science is trying to figure out is how snakes can use infra-red without a big heat issue. There is nothing that humans have designed thus far that has the complexity of their ability but doesn't produce huge heat problems. Mother Nature is a pretty smart broad isn't she LOL.

Your snake was probably reacting to your movement and big heat signature. Just after they've eaten a lot of snakes are still very hyped up. They might not be hungry still but they are their hunting instincts are keyed up and they will react to movement/heat in range of them.