The best advice for sensitivity would be to do balooning. Balooning in a sense you masturbate just by rubbing the lowest areas of your weener at the base, then when you’re on the point of no return - PONR you try to stimulate yourself to have as much as blood as possible in your penis. You’ll get alot of blood and pressure in your dick and it causes somehow the nerves to be more sensitive + you don’t stimulate the upper nerves which are the biggest player in blowjob and penetration feelings. It takes some time to get a grip at the technique but it’ll do exactly what you want. Also masturbating once a day is not good for retaining the sensitivity back - but if you really want sensitivity I recommend to have 2 masturbation sessions without porn (in one day) every 3-4 days (you would also probably have to cut some sex too). After you regain your sensitivity it might be good to do maybe balooning forever. It’s really the sh*t!!!
I started balooning while my gf was in US during the summer and when she returned I coudln’t believe how a blowjob or bareback penetration felt good. OMG I was in total heaven. If I wanted I could have been done in like 5 seconds and I even started moaning. But the more we had sex the less sensitive I was so I again started balooning once in a while between the days we’re together and it keeps me quite sensitive. I felt the imidiate change even through a condom.
Not touching the important nevers on dick so much, not using porn (heck I don’t even use imagination.. i just concentrate on the stimulation feeling) will help your sensitivity alot. Believe this or burn in hell :D