I've had this issue for what seems a few decades. Also swishing in ears under exercise. Had a bit of vertigo over the years and dizziness is common. Lo and behold I recently went to get my ears cleaned and they were both totally blocked with wax. As hard as concrete. I've been a big ear plugs user to try and get rid of the low frequency rubbles. Took two visits to get them suctioned out and now I can hear an an ant fart. Low end in music through headphones has lost its severity or "ooooomph" too so I'm thinking the blockages were tight upto my ear drums and acting not just as a conductor and amplifier of low frequency but also adding pressure to capillaries in that region.

Life changing. Go get your ears checked.