What Causes Numbness In Bottom Most Ribs?

Hi there, I've been experiencing a weird sensation recently. Underneath (and maybe slightly behind) my bottom most left rib there is a feeling of numbness but at the same time it is quite uncomfortable and feels like something is brushing against that part of my body constantly. It makes it quite difficult to sleep, not because I am in pain just because the weird feeling is constant. I have also been feeling a bit lightheaded recently and have been experiencing unusual bouts of what feels like heart burn.