I think it might have happened from sitting actually. lmao
Because I used to use my computer on my big screen, and sit on a really comfy couch as I worked on my sites, and stuff. But not that I spilt a beer on my wireless keyboard, and mouse. I have to use my small monitor and sit in this not so comfy chair. I sat in it basically all day yesterday, and I think that is what did it.
It also might not even be a pulled muscle, I am just assuming it is, and hope that's what it is.