I have social anxiety disorder. I also often zone out for unrelated reasons (say, when I'm really focused on something technical).
My partner mistakes my zoning out for me not being okay, so they ask whether I'm okay or not. I often reply with a distracted "yes", but because the reply was seemingly unconvincing, my partner takes to repeating their question again and again (with me replying with a distracted "yes" over and over).
I find it hard to focus on anything else while I'm engaged with the task at hand (in our scenario, installing software on my partner's computer, while around other people), and as such, I feel trapped when I have to subconsciously keep batting away such repeated questions.
I know my partner means well, and is really concerned about me. How can I politely let them know that I really am okay, such that it is indeed convincing?
 We have been together for a little over 4 months. Admittedly we have a lot more of getting to know each other.
 I have once stopped such a series of repeated questions with a "Yes, I am okay" with my voice raised. I essentially snapped. I felt bad about it and said sorry.
 In response to , my partner told me how their parents often had the same problem, and that their dad always snapped like I did. My partner was afraid that we'd devolve into something similar.
 I have (before ) in the past let my partner know how I am prone to zoning out like this and that I really am okay in such situations. They were unable to identify it when  happened, because a lot of people were indeed around, and they correctly thought that it might trigger my social anxiety (which it didn't at the time though).
We have moved past that incident, and we do love each other a lot, but I want to set up some protocol or signal so that this doesn't end with us feeling trapped.