not sensitive as i should be (i think?)

ok im 19, i have been masturbating since i was 12, and im a virgin though have had some wet dreams, what im concerned about is that im just not affected by anything anymore, when i was 12 i could just see a picture and i would be done but now its like nothing gets me excited at all, and i seem to not produce much, just a dribble...is this bad?

(also i usually masturbate once a day)

Actually i seem to do better without visual stimulation for some reason, if that means anything.

i also feel really guilty afterwards, although i know that its healthy and natural.