Pregnancy hormones, venting!!

So I know I may be over reacting over this but it’s really bugging me. I am currently 9 weeks pregnant with my second baby but my partners first baby, where I am they do the anatomy/gender scan between 20/21 weeks only and my partners has know when this since not long after I found out I was pregnant so it’s not like this date has come as a shock. But now he has decided that he is going to a week long car show event thingy a few hours down the line and doesn’t want me to find out the gender of out baby till he gets back. I have to go for my scan while he is away but he wants to keep the gender in an envelope until the Sunday when he’s back. I told him from the start that waiting to find out the gender is something I can not do and he never asked me how I felt about him going to the car show, never thought about how it’s 5 unpaid days off work, NOTHING. I am also struggling to know if I bring it up to him or if I’m just over reacting but he is autistic as well so confrontation makes him shut down