I very often feel numb as well. Like you, I have 'internal' feelings, but they just don't come out. I feel very sad, annoyed, interested, moved, and anxious, and yet none of this is probably noticed by others, and barely register on my own radar either. It's frustrating and so sad. I used to be such an entirely different person. I am in much better shape in some ways, but I seem to have traded that in for this numbness that just won't go away. The only emotion that is intense is anxiety and even that I think I don't show, or not in an expected way; I just feel a million butterflies smashing against the walls of my stomach and I can't shoo them away.
I think for you, and perhaps for me, it is a medication problem. It is so hard to find that sweet spot where you're taking enough to not go into episodes, but not too much to end up in this state of numbness.
This is why I have fantasies of stopping taking my medications entirely, so I can see my old self reveal itself and be someone far more interesting and fun to be around, instead of so flat. On the other hand, I'm scared to do this, so I don't. I don't want to lose it. And I'm also afraid even to change medications around as this combination has kept me stable for so long. I guess I can feel intense fear, then
I hope you're braver than I and talk to your pdoc about the possibility of changing around your meds so you're not so numb, and so that you can better express how you're feeling verbally, in the moment. Best of luck.