Thanks for writing to H.C.M. for your query.
I have gone through your query regarding reduce hearing in your left ear, and as you said that you feel momentarly better hearing by pressing the tragal cartilage
and as it is released hearing becomes better.
Your this observation of getting better hearing indicates that your eustachian tube is not working properly and it gets block from time to time. To diagnose it you may examined yourself by Impedance Audiometery, which will clear the picture.
As far as reatment is concern you should yourself examined by an ENT specialist
to rule out any pathology in nose , paranasal sinuses
and throat which may cause eustachian tube dysfunction
, if any such problem is identified that should be treated first, on the other hand if nose, nasopharynx
and throat are found to be normal than GROMMET insertion on your ear drum will solve the problem.