I have pretty much the same thing, as does a friend of mine. You say you're good at reading emotions, in which case you can put them on to a certain extent, but I would advise you only do so to a muted extent. Tell people that you tend to internalize emotions and that you hate sympathy (which is actually true for me) and by and large they'll leave you to it and believe you are feeling something. Most importantly, don't tell people that you don't trust 100% that you don't really have emotion. And unless you're the joking type generally, don't do it in the form of a joke.
On a happier note, I guess, maybe one day you will feel some emotion. I went for many years without emotion but I do now have someone I genuinely care for and feel emotion with. Which means I can now just imagine that the situation happened to them in order to identify the correct reaction. So there is a way to move on.