How often did you get morning wood before you started finasteride? (answer this one HONESTLY! If you don't really know, then don't tell yourself that you used to get it all the time)
Is the "reduced sensation" really a giantly noticeable amount? Or, are you possibly just looking for side effects? Remember, if you look hard enough, you'll ALWAYS find something to try and associate with finasteride.
My thought is that the "decreased sensation" might because of the fact that you're worrying so much about it. Before finasteride you would finish off and not give it a second thought. After finasteride you finish off and are probably worrying about it in the process of it! Just that would be enough for me to not enjoy it as much!
However, it's possible (though unlikely) that you are having problems. My suggestion would be to stick it out for 3 months. Just force yourself to ignore it. If you were having serious brainfog and couldn't get it up, THEN I would say to drop it. But, as I see it, it's too early to do that and the (possible) sides aren't bad enough (imo). Remember, a minority of the people have sides, and a vast majority of them stop the sides soon after stopping finasteride.
Hang in there.