Bad night with a partner, feeling useless and traumatised

Context: I am poly/open, so is she, we are basically fwb and have other partners. We have had sex before and sometimes it’s been great, other times meh, but never a problem so far. But I have similar sexual dysfunction with other partners, and think I’m ace/demi

I (25NB) stayed at hers 3 nights in a row and we’d been having a really lovely time, no sex though. she was initiating each time we went to bed, I would give her attention, snuggles but nothing in return because my arousal was literally 0. Not a single sparkle down there 😅 3 nights running.

It was all fine until last night and I was so tired, we went to bed at like 1. she was initiating and I tried to go in with an open mind to see if my arousal would wake up at all, because sometimes it does.. it didn’t though. Instead I got stuck and felt my words leave me and like I couldn’t stop/ end things when I wanted to, nothing actually happened sexually, but I ended up stopping and said I was triggered by past traumas. Inside I just felt useless, like I couldn’t put out / satisfy sexually.

I feel like the expectation is that when there’s a hot person in front of you who you’re into, you fuck them, but I just couldn’t/can’t/don’t want to… and that makes me feel useless tbh because I’m leaving her unsatisfied and probably given her something to overthink/worry about which just complicates sex even more