Owwie stretching … anyone with experience?

I have not managed to get a picture but searching Google or this subreddit will show examples that look identical to my girl’s behavior. In labs they apparently call it “writhing,” where they stretch out long and suck in their sides and twist at an angle.

She’s been doing it on and off for the past half hour. I can’t figure out what triggered it. She tried a piece of spinach for the first time about two hours ago, and recently had a small selection of seeds (sunflower, flax, pumpkin) as a snack. She has choked on a seed in the past but that did not appear to happen this time.

It’s midnight so I can’t contact the vet until tomorrow. I’m just praying that it’s a moving gas bubble or constipation (I witnessed her poop since she started the owwie stretching tho). The only other thing I can think of is that when I went to grab her from under the blanket where she was starting to chew on the couch, that that she pulled a muscle in trying to hold on while I lifted her. She didn’t squeak at the time though. Worried it’s an internal issue like a tumor.

Has anyone had a rat display this behavior and recover?