that I did try it for pain in my right knee/leg - pain is sometimes there and sometimes not.
I did find similar to you - focusing on it, it would sometimes disappear.
which is not what one would expect.
maybe it is the realization or the experience that pain is not the firm, localized, "concrete" phenomenon that we imagine it to be.
I do two meditations daily: one - jyoti and the other mindfulness. (well, actually, mindfulness not daily - but often.
I find them both powerful and transforming, in different ways.
Mindfulness is interesting, and my teacher is great. I am learning a lot.
One thing I'll pass on to you - that my teacher says - no, two things:
1. The mindfulness approach is one of curiosity, and experimentation.
no judgement. She says (maybe this is in the recording, so I may be repeating.), 'when the mind strays, bring it back GENTLY. We are practicing loving kindness with ourselves.'
2. the other thing she says, changed my whole meditation experience! That is, that the treasure of the meditation is that moment when we realize our mind has gone off on its own, and we bring it back. So, it's not that 'oh, my mind strayed 100 times I am having an awful meditation session.'
It's that every time it strays is an opportunity to be mindful.
so - for me - that put a different spin on meditation.
I look forward to reading more about your experience.