You are describing almost exactly what I am experiencing, except for me it is my left thigh-
Localized twitching, perceived weakness & stiffness, what I believe to be atrophy (Skinnier, muscle dents etc). Less flexibility with this leg & longer recovery time after exercise.
I've only seen a GP who did a neuro exam and told me it was totally normal, no referrals. This was a month ago and I'm still in as much of a panic as I ever was & can't shake it.
I don't have too much advice, as I'm a bit of a mess myself at the moment- but our problems seemed to similar for me not to reach out :)