Yes, as we age, things do change with our bodies, to varying degrees. However, since you mention masturbation, you could try avoiding all masturbation and use of porn, so that all of your sexual activities are only with your partner. That way you will notice if masturbation is a factor. It may take several weeks to completely confirm any changes. Also, once a week or so, allow your partner to give you a slow handjob so that you will get a different sensation than from vaginal intercourse to see if there is any difference in your feeling.
You may do some exercise in addition to the above suggestion. Google, male deer exercise, kegel exercise, sat kriya, anal peripheral prostate massage ,While doing intercourse, you can kegel each other alternatively.This will give different sensations to each other. Breathe to orgasm- google this method as well. It helps to expand the orgasm itself.
It's worth a try, thanks for the tip!
ok, thanks. How long til muscle strengthen enough to notice change?