Here's hoping the doc can help.  Keep us informed and thanks for alerting me to this

Are you saying that you ejaculate but have no sensation of having done so ?

By loss of sensation, are you speaking of not as powerful?

(partial) or certain neurological conditions (MS, Parkinsons) can do this. I suspect neuropathy or side effects of diabetes might in certain cases.  I know first hand.  It still happens for me...  but it feels different, little or no warning that it's about to happen.  Tease & deny massage can make it a little more intense.  Frustratingly my urologist wasn't much help.  
Most of the make sexual function meds have to do with an erection & blood flow, not sensation.  Some medications which are used for nerve pain...  interfere with sensation we want to have.  Neurontin comes to mind.    
I will say a patient partner who understands & is willing to do what ever it takes is a great benifit.  I had one long time Favorite, early on we had this discussion.  She said "It won't be a problem" and it never was.  But I would say the proviso that's true IF you can come at all.  

I wish I had something concrete to offer.  Without knowing your medical details, I'd ask if you have loss of sensation, numbness or tingling in your lower body / limbs.  If so nerve conduction testing might help in understanding your symptoms.

Harborview makes excellent points for consideration.

Aside from the obvious neuropathy issues, usually associated with Diabetes - (which also contributes to erectile dysfunction later on, as well), one of the challenges of a maturing body are the physiological changes which include lack of sensitivity in multiple and various parts of the body, genitals notwithstanding.

I hope your urologist had better answers for you. Just remember, your penis is not what your partners are having a sexual relationship with. Your sexuality exists independently of your genitals. Ask anyone who is paralyzed from the waist down. What doesn't work has nothing to do with the sexuality they feel, express or experience. It is just a different stage that it is played out on.