Partner annoyed I wanted to leave early

[MollyE45]

So went to a sit down "party", mostly like a meal, with DP and his family , many of whom I've never met before. There was about 15 of us. After a day at work, I was already tired but DP said we'd stay only until around 9 (meal started at half 6.

The first 3 hours was fine, I was socialising etc. But around 10 past 10 I became tired and I asked DP if we could start getting ready to leave.

He snapped at.me (in a whispery voice) that it is not good etiquette to ask for the bill when nobody else has asked.
I'm not the best socially and everytime DP would go to the toilet, nobody was speaking to me and I felt really awkward. I started feeling quite claustrophobic that I couldn't leave this meal.
I told him I'd been here 3 hours and that was enough for me and I said just because we're leaving, doesn't mean everyone else has to. He sulkingly asked for the bill.

We haven't spoken since coming home last night and I feel dreadful. I don't know why I'm like this socially. I was fine the first couple.of hours but then I just become tired and this seems a regular thing, even as a child I'd want to leave parties early

I hear you OP.
I am a friendly person,I'm the one who chats to people in queue in the supermarket etc so not totally introvert.
But I'm not a social person. I don't like parties or evening diñners out.I find them tiring,
Luckily DH is of the same nature as me. So we always agree a time to leàve and have a plan in hand.

Surely someone has to be the first to ask for the bill or else you stay there until closing?? I think it's fine since you had an agreement in place first of 9.30. However it sounds like dp was having a good time and didn't want the night cut short. It sounds like you're maybe an introvert and people don't always understand that socialising takes effort and energy from introverts rather than it being something to thrive on and be energised by the way extroverts are. You can't pretend to be something you're not and dp knows you and presumably knows you find situations like that overwhelming. I think almost 4 hours is more than long enough to take a table before asking for the bill. I don't mind socialising but my dh LOVES socialising. I remember trying to remove him from a house party at 1am and finally leaving at 3.45am because he had to say goodbye to everyone and I was ready for the hills! We normally agree a time now that we feel is a fair compromise between us both and we stick to it so it doesn't cause any issues.

10PM is plenty late, particularly since the plans were just dinner. Presumably OP had been working since 7 or 8 that morning.

He sounds really scared of his family. There's absolutely nothing rude about leaving at the end of a dinner with, " Here's some money to cover ours, long day at work so we're heading home, nice to see you" etc.

Sitting and watching people get drunk is really dull. Especially when you've been working all day and sat through a meal with relative strangers.

I had a boyfriend did this. Absolutely no off-switch. Even if we managed to leave somewhere on time, he had to stop and see Jimmy and Jane and whomever else on our way home. He was always the last to leave, and then long goodbyes. We broke up after a night very much like yours OP, where I said to him multiple times that I had to wake up at five the next day, so needed to make it an early night. After three discreet mentions from me, I finally ordered myself a taxi and left the venue. Nightmare.