For me, it's like, when something catches my interest in a sexual way, I can feel it. I feel like I'm getting a hard-on and my pants/underwear actually feel tighter, however, when you look, you don't see anything out of the ordinary. It's actually very upsetting, because as a male, I'm a homo...and I'm not the type that likes to take it if you get my drift.
It kills me a little inside to feel that, what I call, invisa-dick and not be able to use it. I want to have bottom surgery, but if I still can't use it, what is the point? I've used toys with my boyfriend, and I do get some satisfaction from it, but it's not the same. He supports me in whatever direction I choose to go with the gender thing, but has stated that he's happy with me as am. He doesn't want to risk my being inable to orgasm just so he can look at a penis.
But I digress... I know what you mean by it just 'being there'. I've felt it all my life, and probably always will.