How to Communicate Extreme Exhaustion to Your Partner?

I could use everyone’s insight and perspective on something. If your normal is a moderate level of exhaustion, how do you differentiate to people you are close to (i.e. partners) when you are exceedingly exhausted? For current context, I’m at a wedding that started at 4:30 p.m. and is expected to probably go until at least 2 or 3. It is also an hour away from where we live. I’ve been here for 5 hours and every part of me is struggling. I can’t even get myself to stand right now, might head is pounding, I feel somehow dizzy and unbalanced, and my brain feels like it’s moving in slow motion. I didn’t go into that level of detail because it was loud, but I said no to going to the dance floor for those reasons. My partner knows I have social anxiety, so I think that in spite of my saying that it was because of physical things, they may have thought it was largely anxiety-driven. I explained that I was exhausted, and they said that I should get up so I wasn’t thinking about it since that’s what keeps them going when they’re tired. I know you just got a small snippet of our relationship, but my partner is truly supportive I’m so many ways. What are your thoughts on how to possibly explain this blind spot in their actions?