I can occasionally feel the earth's energy as well; but not all too often.
As I have come to notice is that this feeling usually comes with being either of the shamans, mediums, and long-time occultists (in a slightly different way).
It also happens with the changing- growing or decreasing- of spiritual energy.
Meaning, it could be because you're a new medium or that your energy has been increasing because of the greater use. This feeling may die after a while as your energy slows and evens out to a certain potential; by then you could start feeling it more because you are medium.
It's rather difficult to pin point the reason for you exactly but my theories should be fairly close.
If I were you I'd meditate on it a for a bit and test the different ways you can feel it.
* Trying different body part like holding your arms and seeing if they pick up anything.
* Trying different places; there are places around the world that emit greater energy fields such as the Bermuda Triangle (don't go there, it's just an example).
* Try grounding and other methods of borrowing spiritual energy that would include sudden bursts of energy on your part and seeing if it either helps you feel more, causes you to feel less, or doesn't do a thing for you.
Those would be good tests to sort6 of pin point anything you should know about this new ability.